SYNTHETIC SOUTH INDIAN MRUDANGA

TEGHMCAL FIELD
The present invention pertains to. Indian percussion instruments in general, and in particular, to .7 apparatus, systems and processes for constructing a synthetic South Indian Mrudanga.
BACKGROUND INFORMATION AND PRIOR ART
. Percussion instruments provide rhythmic accompaniment to instrumental or,vocal music. They
are also employed, in percussion ensembles and as solo instruments in percussion concerts. They
constitute one of the most important classes of musical instruments. Of the various types of
-. percussioninstruments, Membranophones. assume a very prominent place! As the name suggests,
Membranophones. are .those instruments that produce sound via a thin vibrating membrane held
under tension

In. general, sound consists of a fundamental frequency and a number of distinct higher frequencies known as overtones. A harmonic is an overtone that is an integral multiple of the fundamental. Based on this: concept, Membranophonic percussion instruments can be classified into two categories. 17 Instruments that produce inharmonic overtones and 2. Instruments that produce harmonic overtones.

A vast majority of Membranophonic percussion instruments produce inharmonic overtones. Examples include Western percussion instruments such as Tom Tom, Snare drum, Kick drum and percussion instruments originating from other countries, such as Conga, Djambe, Darbuka, Bongo, etc. AH these.percussion instruments essentially have a circular piece of a vibrating membrane that' is pulled over the opening of a hollow shell. (Sometimes multiple sheets are stacked together to form a thicker sheet, enhancing the durability of the drum head.)

Among the Membranophonic percussion instruments that produce harmonic overtones are the kettle drum (also called the Timpani or Tympani) and an array of Indian instruments such as the South Indian Mrudanga, Phakawaj, Tabla, Khol etc. The Tympani produces nearly harmonic

; overtones due to its unique bowl shape and air pressure variations inside the bowl when the drum . head vibrates; Barring the Tympani, there seems to be no other percussion instruments of the harmonic category in the world other than those that originated from India. .

Indian percussion instruments such as the Mrudanga and Tabla produce near harmonic overtones -that operate' on the principle of circularly symmetric loading, which is indeed a.very a unique technique. It was Sir C. V. Raman who first observed that these instruments produce harmonic overtones .due to die process of loading the central: part of the membrane with a material of higher density. The sounds from these instruments are very, musical.and !have'a well defined pitch due to; the presence of the harmonic overtones. The loaded.portion in the Mrudanga is calledthe Karane (Sadham or Soru in Tamil) and Syahi or Masala in the case of Tabla.

The.Mrudariga (also'known by names such as Mridangam or Mrudangam) is constructed using a hollow shell carved out of a single piece of Jack or any other suitable wood, and has drumheads attached to; its.right and left side openings. The right head consists of three membranous coverings. .The inner one is in the form an annual ring with its inner rim slightly projecting into, the opening of the shell; Made of goat skin, thislayer serves to protect the main membrane from, wear and; tear due to friction with the bearing edge of the drum. The middle membrane is the-main vibrating; membrane, also made of goat skin. To the central portion of this membrane a permanent black paste made of a dense material is applied which is knovyn as the Karane. The Karane's constitution has been proprietary with different makers using different formulations. Broadly speaking, the paste consists of boiled rice with heavy particles such as iron oxide or manganese added to increase the density. After it is applied, each layer" is allowed to dry and is then rubbed with a smooth stone until tiny cracks appear in the surface. The patch ends up. with-a slightly convex surface. Although the paste appears hard arid dry it remains considerably flexible over the vibrational amplitude range of the drum membrane. Heavy particles of metal suspended in a flexible matrix of starch, and tiny cracks within the body of the Karane hold the clue to its flexibility. Since the bonding of the paste to the skin is mainly through the starch acting as glue, the particles.of the Karane wither away over time and reapplication of the paste is required every now and then.

The outer-membrane made of cow skin has a circular cutout larger than the Karane. All the layers'are braided, together at their outer edges and fastened to a leather hoop made .of buffalo skin. Small pieces of broom stick are placed around the Karane between the outer and middle . layers.

The.-left head consists of generally three membranes;. The. inner membrane is made of goat skin.
"• two:: thick- layers of buffalo skin each having" large equal-diameter cutouts constitute the outer layers. All the layers are braided together at their outer edges and fastened .to a circular leather
hoop.' .Tension is applied to the heads by means of a long leather thong made of buffalo skin that weaves back and forth (normally 16 times) between the right and left hoops of the drum holding .
the. two heads together. On the left drum head, the inner layer is the main vibrating membrane to.
"-which "semolina paste is applied just before playing the instrument in order to bring, the overall
pitch down. It may be noted that .the left head does not produce pitched, sounds. In fact, the two
outer skins press against the inner most skin preventing it from producing pitched sound referred
- to as ringing. The tension of the left head (the inner vibrating membrane) cannot be varied and
the pitch can only, be lowered through the application of the semolina paste. The outer layers
offer rigidity to the left side and.the Mrudanga can be stored upright with the left head placed on
ground; The head produces un-pitched bass sounds and facilitates playing of the glissando type
of sounds known as Gurhki-s. . .

The size of the Mrudanga varies with the pitch. High pitched Mrudangas suitable for female voice accompaniment are about 22" tall with the right head diameter of approximately 6". The low pitched ones suitable for male voice accompaniment are about 24" tall with the right head ■diameter of approximately 6%M. The left heads are a'bit larger in diameter than the right heads. .

The art of Mrudanga making has virtually remained the same over centuries excepting for some
' minor improvements in the process and selection of materials. One such improvement is the use
• of synthetic Nylon straps instead of leather thongs" to hold the heads together and provide the
required tension to the drum heads. The Nylon strap is strong, durable and aesthetically, more
pleasing than the leather thongs.

Another improvement witnessed, in recent times is the use of threaded hooks, huts and tuning; lugs that are used in place of the leather thongs'. Such a Mrudanga is commonly referred to as a "nut-bolt-* Mrudanga: The lugs are small metallic pieces that are threaded into the Mrudanga* s wooden shell. Each lug has.a hole at the.exterior end through which the threaded bolts can pass, through:The hooks' are attached to.the braided hoops and the threaded end is passed through the .'
.holes in the lugs. The .threaded hooks are men tightened with nuts using'a spanner as a tool. With-
. this aiTangemeht itbe . . ' .

-Recently, there'have been further improvements made to the above. The hooks are replaced by. eyebblts and a Nyion strap. The Nylon strap runs through the eye bolts and the braided hoops forming a complete loop; in such a way that the threaded eye bolts can pass through the lugs on the shell. Tightening is accomplished in the same way as in a hut-bolt Mrudanga. The advantage of this system is that, the braided hoops are less susceptible to damage as the" pressure is distributed more uniformly by the Nylon strap. Moreover; the tuning range of the Mrudanga is also'increased considerably.

Yet another improvement is the use of a permanent black paste for the left head. This eliminates the heed for using a wet.semolina paste each time the Mrudanga is used. However, this method, has been, used only by. a handful of percussionists.

The traditional Mrudanga constructed this way has many disadvantages:

1. The necessity of using animal skins for its construction implies that the animals involved namely the cows, buffalos and goats have to be slaughtered. Most of the practitioners of .■ this.art really do not want to hurt the animals but as there is no choice at present they are constrained to use these products requiring animal slaughter.

2. The Jack wood required for the shell is not available in sufficient quantities to meet the market demand. Cutting of the Jack wood tree is also banned in some Indian states: This . has led to illegal felling of Jack wood trees. In general the shell requires cutting of large trees which is detrimental to the environment.

3. The heads aire hot detachable. So if the headshave to be serviced, the entire instrument has to be.transp'orted.tp the service shop.

4. They are in general heavy and hence difficult to transport.

5. Mrudangas are'manufactured by different craftsmen in'their own ways using materials and processes that are held as closely guarded secrets: This results in nori standard
.. materials, processes, and dimensions adversely affecting tonal quality, reliability and supply.

6. Manufacturabilityis a major issue with traditional Mrudanga "Craftsmanship that uses
animal skins.whose properties vary widely from sample to sample. The wooden shells
"/also vary widely, in composition, texture, moisture content and tonal quality: The
. manufacturing process is highly labor incentive and has a huge negative impact on the
environment.

7., The pitch of the instrument is susceptible to variations in temperature and humidity:

8. The black paste, Karane, is mechanically bonded to the main vibrating membrane using
starch as glue. This results in the gradual withering of the black paste leading to loss, of
tonality.

9. ■ The left side head requires the application of semolina paste each time the instrument is
played. The semolina powder is first made wet, kneaded into a thin paste and applied at - the centre portion of the left side head. After the playing session it has to be scraped off from the head. This is a messy process and limits playability of strokes and glissandos on the left head. ...

10.. The left head has a cut out on the outer skins made of buffalo skin. These cuts can cause injury to the left hand-while playing the glissandos.
In view of the above drawbacks it is apparent that there is a need for a synthetic Mrudanga that is ethical, does not require felling of trees, impervious to weather conditions, light weight, durable, easy to maintain, and easy to play.

To date, the bnly Indian percussion instrument belonging to.the harmonic category that has been .made with'syritnetic materials is the Khol, which is a two-sided drum originating from the Indian states of Assam, WestBengal and Manipur. It is mainly used^as an accompaniment to devotional music. A completely synthetic version of the. Khol, known as the Balram orTilak Mrudanga-has ■ been developed and marketed. These are mainly used by the ISKCON devotees..However, this is a "much simpler instrument compared-to the south Indian Mrudanga which is the subject matter of this invention. Some of the major differences between the Khol and the South Indian Mrudanga are

1." The Khol uses a single layer of.skin on its left and right heads whereas the South Indian Mrudangaruses multiple layers-3'layers on the right and 2-3 layers on the left.

2. The tuning requirements of the right head are not stringent in the Khol whereas it is extremelystringent for the south Indian Mrudanga.

3. In the Khol the right head is.very small and it produces a high pitched sound. It is generally not tuned to any specific pitch whereas in the Mrudanga the right head is much ■ wider and i s turted to the tonic of the drone or reference pitch.

4. In the Khol the.pitch of the right head is hot aligned at'all points on its periphery as'the head is too small whereas in the Mrudanga it is aligned to the tonic of the drone or reference pitch at all points on the periphery

5. The Mrudanga incorporates pieces of broomstick between the layers to produce special sounds which the KhoJ Jacks.

6. The Mrudanga is generally played by highly skilled and professional players which demands extreme. accuracy of tuning, tuning stability and tonal control suitable for classical music whereas the Khol is played by semi- skilled or unskilled devotees as an accompaniment to devotional music.

SUMMARY OF THE INVENTION

The present invention pertains to a completely synthetic South Indian Mrudanga that is suitable for use in Karnatic music concerts, percussion solo and ensembles, fusion music, bands, classical dance recitals such as Bharatanatyam and Kuchipudi, film music and light music The word "synthetic" used here refers to man-made materials that do not exist naturally, such as plastics arid.rubbers derived from petroleum and other chemicals, while clearly excluding animal.derived products.

■ The present .embodiment eliminates the need for using any animal skins. This is achieved." by^ . :■ using/synthetic'. materials to construct the drum heads. The right head consists of three membranes of synthetic materials serving the same purposes as in the traditional hide Mnidanga. "The middle layer has the loaded portion called the Karane which is bonded to the vibrating ; ..membrane, through-.a. chemical, bonding process. It is this Karane that imparts to it the .characteristic tone of the Mrudanga. Below if is a membrane that is in the form of an annular -. ring.' This membrane is not visible but serves the purpose of protecting the main membrane from ..'..'. wear and.tear. The top-membrane is in the'form of a circular disc with a cut put.slightly larger ' than'the Karane. Wheh'ihe head is assembled, the Karane projects out of this cutout. To.emulate ".■ the broom stick pieces, special plastic strips are bonded to the inside of the top.membrane. These .,: . strips, produce the typical "Chapu" sound of the Mrudanga.
the left, side consists of the same layers as in the conventional Mrudanga but with two improvements. An additional inner membrane in the form of "ah annular ring is used, to protect : the main membrane.from wear and.tear. Also the semolina paste is completely eliminated. The required loading to lower :the pitch is provided on the inside of the membrane, so that the entire playing area on the outside is available which greatly enhances the ease of playing the left hand strokes and the Gumki-s. The left side head is covered partly at the rim by a plastic casing that is specially profiled at the inner edge to facilitate easy gliding of the hand during Gumki playing.

Each drum head is provided with a set of metallic clamps that are used to attach the drum head to the shell via-bolts and nuts and tune it. Tuning is accomplished using a spanner provided with the instrument. The heads are fully detachable and can be replaced by the user.

Yet another feature of the present embodiment is the use of fibreglass shell instead of wood. Fibreglass is a well known material suitable for percussion drums. Both Western and Indian musical drums have been constructed using fibreglass. The shell is constructed using a moulding

■. tool and a hand layup process. The use of fibreglass as the shell material has a twofold advantage; .. First, ;it eliminates,the,need for cutting the trees for wood. Secondly it is, much easier to process - fibreglass as it'an engineering material. The fibreglass"also results in a lower weight product with . enhanced transportability.

The present, invention also enables standardization and tonal consistency. The use of engineering . materials, precision tools and controlled processes results in enhanced tonal quality, consistency, reliability and supply..

Manufactur'ability -is. greatly improved using the processes, tools, and materials of the present : invention. The. shen/drum heads,- and other component parts can be mass manufactured in . industrial settings, greatly eliminating the need for manual labour and processes.

BREIEF DESCRIPTION OF THE DRAWINGS
.
Fig. I depicts the isometric view of the fully assembled Mrudanga.

Fig. II shows the elevation view of the Mrudanga when the covers are removed.

Fig. Ill depicts the plan view of the right side and left side lug rings along with the isometric view of the clamp and the elevation view of the back plate for the clamp.

Fig. IV illustrates the bross sectional view of the.drum shell and an elevation view of the drum shell with the lug rings attached.

Fig.V shows the plan views of all the membranes of the right drum head before assembly and after assembly:
Fig. VI depicts the plan views of all the membranes of the left drum head before assembly and after assembly.

Fig. VII depicts the plan views of the right and left drum heads after assembly and bending.

Fig. VIII shows the top (plan) and cross sectional views of the right side and left side covers.

Fig. IX shows all the components that go into the assembly of a complete Mrudanga.

It should be noted that while each of the drawings are drawn to scale, the scale factor is not maintained from one drawing to another due to constraints imposed by the need to group logical entities-together and provide more details of certain components.

DETAILED DESCRIPTION OF THE DRAWINGS

Fig. I shows the isometric view of the fully assembled Mrudanga consisting of the'shell 1, the right drum head 4, the right side cover 6 and the left side cover 7. Also seen are the circular black . patch known as the Karane 12 and the cutout 32 on the outer membrane of right drum head. The ,.drum .heads; are. attached'to. the shell-with the help, of nuts 17 and tension bolts 16. Also seen, partly are.the left side lug ring 3 and its.projections. The covers are fixed to the corresponding lug rings using screws 18; For the sake of completeness the left side view with the circular cut put.is illustrated using dashed lines as this part is actually not seen.

Fig. II shows the front elevation view of the Mrudanga when the right and left side covers 6 and 7are removed: This view shows the shell 1, the right drum head 4, the left drum head 5, the.right lug ring 2, left lug ring 3, the drum head clamps 8 and the nuts 17 and bolts 16 used for attaching the drum heads to.the lug rings. The lug rings 2 and 3 with tapped holes 37 are attached to the shell using bolts" 41 that pass through the shell and tightened with nuts from the inside of the shell. This attachment of the heads to the shell is done by passing the bolts 16 through holes in the. clamps 8 and though the holes oh the lug rings 2 and 3. Nuts 17 not only serve to secure the heads to the shell, but also allow the drum heads to be tensioned as desired. The drum shell has recessed portions 44 such that the bolts 16 and nuts 17 can protrude into them. This recessed portion also facilitates the insertion of a spanner for loosening or tightening the nuts 17 for the purpose of head attachment and tuning.

The clamps 8 are attached to the drum heads 4 and 5 using the holes on the clamps, the back plates and the sheets constituting the drum head and riveting or bolting all of them together. This way of fastening the clamps to the drum head sheet ensures that the drum head sheets are held together and securely attached to the clamp preventing the sheets from tearing when the drum heads are tightened. This contact pressure is extremely important in maintaining the structural integrity of the drum head.

Figures IQ(a) and IH(b) show the plan views of the right and left lug rings 2 and 3, respectively. The projected portions 38 have holes 11 through which the tension bolts 16 can pass. Holes 10 are used to attach the lug ring to the shell through a set of appropriate fasteners. Tapped holes 37 are provided so as to.eriable fixing of the covers 6 and 7 to the lug rings using screws 18.
Several alternative embodiments of the tuning lugs are possible. As an example of such an embodiment; the lug .rings can be eliminated and individual tuning lugs can be fastened to the shell body directly.- ■

Fig. III(c) shows the isometric view of the clamp and Fig. 111(d) shows the elevation view of the back plate that is used along with the said clamp. The clamp has hole 40 through which the tension boh 16 .passes. Holes 39 serve to rivet the clamp and the back plate to the sheets constituting the drum heads. It is also possible to attach the'clamps and back plates to the drum head sheets by other mechanisms such as fastening with nuts and bolts.

Fig. IV(a) shows the longitudinal, cross sectional view of the shell. In the present embodiment a fibreglass shell is. used but shells with other types of materials such as wood, acrylic and other materials are possible. The shell has two necks-the right neck 45 and left neck 46. The neck has a recessed portion 42 which provides the space for the back plate 9 and the heads of the rivets 13. The lug rings fit over the step 43 and the recessed portion 44 provides the space for the bolts 16 and nuts 17 to protrude into. This recessed portion also facilitates the insertion of a spanner for loosening or tightening the nuts 17 for the purpose of head attachment and tuning. The shell attains a maximum diameter at a certain distance along .the axis of the shell. This maximum diameter region .47 occurs closer to the left head and is generally called as the belly portion of the shell. Fig. IV(b) shows the front elevation view of the shell with the lug rings 2 and 3 attached using screws 41. When a fibreglass shell is used additional reinforcement of the lug . rings to the shell is possible using glass and the resin materials.

Figs. V(a) to V(f) illustrate how the right head is assembled before being bent to the required shape.
There are three layers of sheets. The inner most layer 19 shown in Fig. V(a) is in the form of an annular ring with cutout 31 and is made out of commercially available polyester film, known as

BOPET, 190 microns thick. It may either be transparent or semi transparent (milky white or lightly shaded). This sheet has holes. 15 for fixing the clamps. The main vibrating member 20 is shown in Fig. V(b). It is also made of a polyester film but is sold under the Brand names Mylar, Melinex or. Hostaphan. What is used here is a Mylar brand film, 190 microns thick. This sheet toohas holes.15 for fixing the clamps 8 withthe back plates 9.

At the centre of the sheet is a circular disc 12 .of silicone rubber cast permanently on to the membrane. A similar patch is also cast on the other side of the sheet, identical in size and shape to the top layer silicone rubber and formed exactly below .it: This process of casting is described separately under the heading "complete process specifications".

The. next layer constituting the right.drum head is the top layer 21 with a circular cut out 32 shown in Fig. V(c). This layer is made of .the same material as that of the main membrane. The back, side of this sheet has a different construction 22 as shown in Fig V(d). Small strips 14 made of Polypropylene are stuck radially around the cutout 32 using a pressure sensitive thin adhesive tape. A special tool has been developed for locating the Polypropylene strips and bonding them to the fop sheet.

It is important, at .this juncture, to describe the role of these strips. These strips are responsible . for the production of a very special tone of the Mrudanga known as the "Chapu", identifiable by a very distinct "crackling" sound. This sound is produced by striking the Karane forcefully with the little finger. The playing position is such that the little finger is placed so as to extend from the outer edge of the Karane towards the centre.

The pieces of plastic strips play a very important role in the production of this sound. When the drum head is struck, the middle and top membranes start vibrating together. During certain phase of vibration they come together and during the other phase they move apart. The plastic strips play the role of spacers and facilitate these vibrations. During the phase the two membranes are moving apart they vibrate freely and produce maximum sound. During the phase they come close, they collide with each other with the strips acting like brakes to stop the sound. This reduces the sound intensity considerably. However, the vibrations do not stop completely because of the momentum of the membranes. In the next instant they are again moving apart

■ producing sounds of .higher intensity. .The process! repeats itself until the sound damps out ' completely and bedomes un-audible. This amplitude modulated sound gives us a perception of the distinct Chapu sound of the Mrudanga.

Reverting-back to the construction of the right drum head,\ve now have three sheets constituting
the right drum head. The bottom sheet' 19,- the middle sheet 20 which is the main vibrating layer
with double, side silicone casting,, and the top sheet 21 with strips 14 made of Polypropylene
attached on the" underside. The Polypropylene strips are attached radially around the cut out 32
leaving small gap of .1 mm from the cut out. The middle sheet is placed over the bottom sheet
such that the. silicone with black pigment faces the top. Above these two sheets, the third sheet
- 21 is placed such that the polypropylene strips: 14 are on the underside (viz., touching the middle
sheet) and the black silicone casting projecting out of the cutout 32. All the sheets are riveted
together using clamps 8, the back plate 9 and the rivets 13; A riveting tool designed specifically
.for this.purpose is used for riveting the assembly. The top view 23 of the assembly is shown in
Fig. V(e) and the bottom view of the assembly 24 is shownin Fig. V (f). The process of casting
and forming the drum head to shape is described separately under the heading "complete-process
specifications".

Figs. VT(a) to VI(f) illustrate how the left head is assembled before being bent to the required shape.

The. left drum head has three layers of sheets. The inner.sheet 25 shown in Fig. VI(a) is in the form of an annular ring with cutout 33 and is made out of the same material as that of the inner layer 19 of the right head. It may either be transparent or semi transparent (milky white or lightly shaded). This sheet has holes 15 for fixing the clamps. The main vibrating member 26 is shown in
Fig. VI(b). It is also made of Mylar film, 190 microns thick. This sheet too has holes 15 for fixing the clamps 8 with the back plates 9. A silicone casting 27 is applied to this membrane using' the process described in detail under "complete process specifications". However, the main differences are (1) the silicone is applied on only one side, (2) There is no need for any pigment to be mixed to the silicone as the silicone patch faces the inside of the Mrudanga.

The top sheet 28 bf the left drum head is shown in Fig. VI(c). It is also made of BOPET, milky white or clear, 250 microns thick: The sheet 28 has a cutout 34.

We thus have three sheets constituting the left drurn.head-the bottom sheet 25, the middle sheet 26 which, is the main vibrating membrane with single side silicone casting, and the top sheet 28. The top vi'ew"29 of the unbent left drum.head is shown in Fig. VI(d). The middle sheet is placed over the bottom sheet such that the silicone faces the bottom. Above these two sheets, the third sheet 28 is placed. The top sheet; 28 is made of a thicker material because it would prevent the left head from ringing. Ringing is a phenomenon of a drum head producing a well.defined pitch. The left head should be capable of producing an overall bass tone and it should not produce a definite pitch because this pitch.would interfere with the right head pitch. Thus this membrane'is very important, as it prevents the undesirable ringing of the" left drum head. All the sheets are riveted together using clamps 8, the.back plate 9 and the rivets 13. The top view 29 of the assembly Is shown in Fig. VI(d) arid the bottom view 30 of the assembly shown in Fig VI(e).

Figs. :VII(a). and VTI(b) illustrate the top views of the bent right drum head and left drumhead respectively. The process of casting and forming the drum head to shape is more fully described under the heading "complete process specifications". Note that wrinkles are formed on the sides when the drum heads are bent from flat sheets. Fig Vll(a) shows the top view of the drum head with the Karane 12 showing up through the cut out 32 on the top layer. Tension bolts are passed through holes 40 on clamps 8 and the lug ring 2 to secure and tension the drum head. Fig Vll(b) shows the top view of the left drum' head with the cutout" 34. Tension bolts are passed through holes 40 on.clamps 8 and the lug ring 3 to secure and tension the drum head.

Figs. VHI(a) and VIII(b) illustrate, respectively, the top view and the cross sectional view (through the diarheter) of cover 6 for the right drum head showing the opening 35. The cover is introduced from the right side and attached to the tapped holes 37 located on the projections 38 on the lug ring 2 using screws 18. The. side cover conceals the clamps and other fasteners from view and gives the instrument an aesthetically pleasing look. It also functions as a support to the hand and fingers while playing on the right head. The left side cover 7 plays a similar role for the left head. Figs. VIII(c) and VHI(d) show, respectively, the top view and the cross sectional view (through the diameter) of cover 7 for the left drum head showing the opening 36. The cover is

introduced from trie-left side and attached to the tapped holes 37 located on the projections 38 on the lug'ring 3 using screws 18. The left'side coyer conceals the clamps arid other fasteners from view and gives the instrument an aesthetically pleasing look. It overlaps with the left drum head covering a part of it and exposing only a portion of the drum head corresponding tbthe cut out portion 36; The left side.cover provides an annular ring like-platform to store the instrument in the upright positioh.by resting against the ground. The cut out area 36 is used for playing stokes and Gumki-s. Both the side covers are fabricated with Polypropylene as the.raw material and using injection molding tools.

The complete assembly process is described schematically in Figs. IX(a) to IX(h). Fig. IX(a)
: shows the drum shell 1 with the right lug ring 2 and the left lug ring 3attached. The shell comes
attached, with.the lug rings from the fibreglass manufacturer. The right drum head 4 and'the left
drum head 5, shown in Figs. IX(b) and IX(c).'respectively, are fabricated separately, and kept
ready for assembly. .The set of bolts 16 shown in Fig. IX(d) together with the .set of nuts 17
shpwn.in Fig IX(e) are used to attach the drum heads 4 and 5.to the shell. The bolts'16 used here
are special bolts with square heads instead of the regular hexagonal heads.'A square head bolt
has a considerably longer dimension along its diagonal than a hexagonal head. The hole 40 in
clamp 8 is located in such a way that it prevents rotation of the bolt when the drum head is
tightened or loosened using nuts 17. The right side cover 6 is then attached to the right side of
the shell and the left side cover 1 to the left side of the shell, using the set of screws 18 shown in
IX(h). This completes the assembly. The covers extend only up to the edges of corresponding
lug rings while allowing part of the bolts 16 and'the nuts 17 occupying the recessed regions 44
be readily accessed. With this arrangements the heads can be tensioned easily using a standard
spanner. '

It will be appreciated that, although specific embodiments of the invention have, been described herein for the purposes of illustration, modifications may be made without deviating from the spirit and scope of the invention as defined by the appended claims.

COMPLETE PROCESS SPECIFICATIONS

( i ) As stated earlier, at the centre the middle membrane of the right head a circular disc made of an elastomeric material, called the Rarane, is"cast permanently on to it. A similar disc is also cast
on the other .side, of .the same sheet, identical in size and shape to the top layer elastomeric .: . material and formed exactly below it.' A circular elastomeric disc is also cast at the.centre of the
middle membrane of the left head.

(ii) The elastomeric material used' for this application is a commercially available' silicone adhesive sealant generally known as a silicone caulk. It is known asRTV-1, meaning Room Temperature Vulcanizing. It is a 1-part system and vulcanizes or cures at room temperature in about 48 hours using the moisture present in the atmosphere. Curing is a process of solidifying where the molecules of the material cross link with one another forming a more rigid structure. The material is generally used as a sealant in buildings; but is an excellent candidate for the present application. What is used here is .the MOMENTIVE silicone adhesive sealant /S 9188. Other silicone sealants are also possible but some of these products may form wrinkles upon curing, which is not desirable. This silicone sealant which is like a paste and highly sticky is deposited in the required measure on to the centre,of the polyester film placed in a special jig and a polythene sheet, is placed over the silicone uncured mass and a tool presses and shapes the silicone mass to the required shape. Once the silicone cures, the polythene sheet is peeled off from the patch. It may be noted that the silicone rubber cannot be tooled directly as it sticks to the tool itself. That, is why a polythene sheet is required between the uncured silicone mass and the shaping tool.

(iii) Depositing the silicone sealant from the original tube onto the polyester film is not an easy process because once the original tube is cut and the dispensing starts, the sealant within the tube starts curing. By the time the silicone patch is cast on the first few sheets, the unused sealant in the original tube would have already cured rendering the entire tube useless. Thus it is imperative that that the silicone must be transferred to a smaller container in a low moisture environment and also stored in a low moisture environment to prevent it from hardening. This smaller container should be opened just before the casting starts.

(iy). In order to properly dispense the silicone, first it has to be .transferred from the original caulk container to an injection syringe (commercially available medical syringe)- This process of transferring the uncured silicone is done as follows:

(y) A dry air. glove box is used for this purpose." It has.two glove ports through which hands can ■ be placed.inside the glove box for doing various jobs without breaking the containment. The .glove box is also equipped with a-battery operated huniidity indicator and a polythene.bag sealer which is operated using AC mains electrical outlet. The power cable of the polythene bag sealer is taken out of the glove box using a-sealed; port located on the sidewall of the; glove box.-. The .glove box has a- top. rim, a rubber gasket and a transparent acrylic lid. Before the start of the process,-the lid is opened and ail the required materials are put into the glove box. The lid is then closed with several screws provided on the. top rim of the glove box with the gasket in between the acrylic lid and the top rim. Once the screws are tightened, the gasket provides an air. tight seal.

(vi). The materials put in to the glove box are- perforated canisters of dried silica gel, silicone caulk tube, its nozzle and the caulking gun, small polythene bags, a few large polythene bags, injection syringes (with the steel needles and pistons removed and stored separately for later use) ■ a knife, a. mini hacksaw blade and a scissor. The silica gel canisters are placed at the corners of the glove box and the lid is closed. The glove box with all the materials inside is left alone for a few hours .for the air to get dry. The silica, gel absorbs the moisture from the air contained in the glove box arid once the moisture reduces to a prescribed humidity level as indicated by the humidity meter, the process of transferring the silicone paste from the caulking tube to the injection syringes can start.

(vii) With the hands in the glove ports, the caulk tube is first mounted on the caulking gun and its threaded tip is cut at the top using the hacksaw blade or knife. The nozzle is then cut to size and screwed onto to the open threaded tip. A syringe is picked up and the caulk's nozzle is introduced partly in the opened syringe and the sealant is pushed in to the syringe till the required volume of the sealant is filled. This volume can be read from the graduations on the syringe. After this, the syringe with silicone paste is put in the small polythene bag and the open end of the bag is then sealed. The process is repeated till all the syringes are filled with the
silicone paste and sealed using the heat sealer. The caulking tube is then removed and sealed in the large, polythene-bag and stored for later use. It can remain in the glove box' itself till'• subsequent use. The' acrylic lid is then removed and the sealed polythene bags with the silicone ' . -. filled injection-syringes are quickly taken out for subsequent batch processing. The. lid is again closed quickly and tightened to provide a sealed containment. Some moisture would have entered'but the silica gel will reabsorb this moisture once'again and keep the chamber dry. Note that-in .this.'process the silica gel itself is protected from absorbing excess, moisture. During subsequent .use, the lid is opened. and the silica gel canisters are taken out of the box for removing the. moisture from the gel by heating them in an oven for a specified time. After the canisters-cool,"they are put back into the glove box along with the other materials! If a new: sealant tube is required that is also put into the glove box. The entire process is then repeated.

(viii) The silicone is-first cast using the above process on one side of the Mylar sheet which will become the top layer 20. As the sealant is white translucent, a black pigment known as SILC PIG from SMOOTH ON is mixed to this to render it black. The pigment is used .in very small quantities, so it would not affect the properties of the silicone: The black pigment gives the Karane a black-appearance as in a traditional Mrudanga. The casting is done using tools developed for.this purpose. After the casting is done, the Mylar sheet with the silicone and the polythene sheet is removed from the tool and allowed to cure for 40 hours at room temperature. After this the polythene sheet is removed and the silicone is allowed to cure for another 8 hours at room temperature.

(ix) Next a similar casting is done on the other side of the sheet using the same process and tools as above. Since this patch appears on the bottom side there is no need to mix any coloring pigment as this side is not visible from outside. The distribution of the Karane mass on to two sides of the sheet greatly enhances the tonal quality as compared to the case when the entire mass is deposited on one side of the sheet only.

(x) An additional processing is required for the top silicone patch. One of the properties of silicone rubber is that it has a very high coefficient of friction. So, when the percussionist plays on the top drum head, his. hand movement becomes highly restricted due to friction offered by the silicone Karane.

(xi) To solve this problem a special ahti friction coating is applied on to this top silicone patch, the. anti friction coating is MEDIO- 6670 from NUSIL TECHNOLOGIES. The coating is
•'applied'..on the silicone patch and cured at 150 degree C. for 5 minutes. Since the Mylar filrri would deform severely at this .temperature, the sheet is placed between two thick Teflon sheets with a circular cutout on one of them such that only the silicone patch is exposed through the cut out during heat-treatment. The sheet isthen removed, and kept aside for further processing. Note that there is no heed to-.apply the ahti friction coatirig.tp the.silicone patch on the other side of the

■ sheet which faces, the inside of the Mrudanga when me drum head is mounted. Likewise there is rio.need to apply the antifriction coating for the silicone patch on the left drum head."

(x) After the silicdnecasring and application of the anti friction coating in case of the right head, the drum .head membranes are arranged one over the other, and are riveted to clamps 8 and. back plates 9'with rivets 13 using a riveting tool in such "a way that the membranes, are sandwiched betweenthe clamp and the back plate. The contact pressure between the metallic clamp and back plate holds the sheets together very securely.

(xi) After'this, the drum heads are formed into shape using bending jigs and applying heat. First, the drum head is bent in a.bending jig. The drum head along with the jig is then put in .a hot air own to permanently deform the drum head to the required shape. To avoid the heat damaging the head, the top and bottom faces of the drum head are covered by thick polypropylene discs serving as heat insulators, exposing only the sides. This process is applied for both the right and left drum heads.

WHAT IS CLAIMED IS

1. ■ A synthetic South Indian Mrudanga comprising:
a drum shell having two apertures at its two ends, a right aperture, and a left aperture, with the said apertures being parallel to one another and perpendicular to the axis of the shell;
the drum shell having lug rings attached to each end of the drum shell a little distance away from the respective apertures to facilitate attachment of drum heads;

a synthetic right drum head covering the right aperture and having clamps at the "sides for. attaching to the drum shell via the right lug ring;
a synthetic left drum head covering the left aperture, having clamps at the sides for ...attaching to the drum shell via the left lug ring;
a.pluraiity of tension, bolts and mits for attaching the drum heads to the shell;
side' covers for the two ends of the shell for concealing the clamps and providing support for the hand while playing the instrument.

2: The 'drum of claim 1, where the synthetic right drum head has three membranes comprising::
an.iiiner membrane in the form of an annular ring;
a middle membrane that has a circularly symmetric loaded region at the centre capable of.producing harmonic overtones when assembled, mounted on the shell, and tensioned appropriately;
.an., outer membrane with a circular cutout larger in diameter than that of the circular loading of the middle membrane, capable of producing the characteristic "Chapu" sound of the Mrudanga when assembled, mounted on the.shell, and tensioned appropriately;.
a.pluraiity of clamps for fixing and tensioning the drum head to the shell.

3., The drum of claim 1, where the synthetic left drum head has at least two membranes comprising:
a main membrane that has a loaded region capable of producing a low pitched bass tone;
a thicker outer membrane with a circular cut out;
a plurality of clamps for fixing and tensioning the drum head to the shell.

4. The middle membrane of claim 2 in which the circularly symmetric loaded region at the centre is made of an elastomeric material that is bonded to the membrane.

5; The main membrane of claim 3 in which -the'loaded region at the centre is made of an . ■--. elastomeric material that is bonded to the membrane.
6. The elastomeric material of claim 4 wherein an anti friction coating is applied for the outer part for reducing the friction between the hand and the loaded portion while playing the drum.
7, The outer membrane with a circular cutout of claim 2 in which small strips made of a. plastic material are stuck radially around the cutout on the underside of the membrane for.producing the characteristic "Chapu" sound. ..

8. The drum of claim 1, where the tension bolts have square heads to prevent the rotation of .the said bolts while the drum head is tightened or loosened.

9. Casting the elastomeric material onto the vibrating drum membranes constituting the drumheads using the process of:
first transferring the uncured elastomeric material to an injection syringe in a dry air . . glove box, transferring the said injection-syringe to a polythene bag and then heat sealing "the polythene bag,
depositing the uncured elastomeric material contained in the injection syringe above to the main membrane, and
keeping the said membrane in a jig and covering the elastomeric material with a - polythene sheet,
using a circularly symmetric shaping tool to shape the uncured elastomeric material to acquire a convex profile that is complimentary to the profile of the shaping tool,
allowing the elastomeric material to cure under room temperature for sufficient duration,
peeling off the polythene sheet from the surface of the partially cured elastomeric material and finally,

allowing the'partly cured-elastpmenc material'to cure completely under full exposure to atmosphere..

10V Syntheticyefsiqnof any of me other iratruments that produce harmonic overtones such' as the Tabla, Phakawaj, Naal, Maddal (or Maddale) or any other drum that uses the 'process of castihg.an elastomeric material on a vibrating membrane described in claim 9.