The mridangam is a percussion instrument being used for millennia in Indian classical music. To call it simply a two-sided drum is to do it injustice since maestros who play it can actually make it ‘sing' by producing a rainbow of sounds and tones. The late Palghat Mani Iyer was one such master and Sri Umayalapuram Sivaraman is perhaps the greatest Mridangam player today.
Acoustic spectrum
How does this simple-looking instrument produce such an acoustic spectrum? This question has attracted the attention of scientists such as C V Raman, B S Ramakrishna, R B Bhat and T Ramasami. Happily, Dr. Ramasami (who headed the Central Leather Research Institute or CLRI, Chennai and is currently Secretary, Department of Science & Technology, India), along with Dr. M. D. Naresh of CLRI, has been collaborating with Sri Umayalapuram Sivraman for the past several years in understanding the roles of each part of the mridangam in contributing to the sound and tonal quality of the instrument. They presented the results of their six-year-long study in a joint lecture entitled “Science for Musical Excellence” at Bangalore on 12th September 2010. While the musician played the mridangam, the scientists explained the results of their analysis – it was thus a jugalbandi of art and science.
Asymmetric cone
The common mridangam is an asymmetric wooden cone, usually 24 inches long. On one end it is 6.75 inches wide and 7.75 on the other. In the middle (actually a bit off centre) it is 9.8 inches tall. This special conical shape of the box seems important for its acoustics. The tonal quality of the instrument varies with the size and the manner of construction. While the player showed how by using different instruments, the scientists showed their analysis of the density, hardness and tensile strength of the wood and the skin used, and fast fourier transform (FFT) analysis of the sound frequencies.
Of the four woods used to make the instrument-jack wood palmyrah, red sanders and cassia, the Ramasami-Naresh analysis revealed jackwood to be the optimum choice based on its density, hardness and good ‘sound radiation coefficient'.
Animal skin is used to cover the two sides of the instrument, so as to produce a sound resonator column within. Which animal skin is the best? Comparison of cow skin and goat skin (the two common ones) showed the latter to be superior: it offers the highest strength for a given thickness.
Its compaction and tensile strength seem to have a special role. The average diameter of its fibre bundles are a third of cow skin fibre (25 versus 85 microns). Where the goat comes from also seems important – limed goat skins for Eastern India appears best. But to attach the goat skin parchment to the wooden cylinder, the best strings appear to be made of buffalo hide.
In a mrindangam, a black patch of material is stuck on the skin for constructing the playing area. This black patch offers tonality. Analysis shows it to have inorganic materials as fillers and adhesive.
Sand is the commonest filler. Rice paste is used to make the patch, along with thin and ultra thin sticks (coconut-based). It is the composition of the black patch, the number of layers in it, the particle size, composition and constituents that determine the tonal quality or the elusive term “Nadham”, the personality of each instrument. Expert players work with the instrument makers in applying the patch, and thus create their personal signature ‘Nadham' and instrument.
And it is here that scientific analysis of the sounds coming out of various compositions and thicknesses of the patch provides important data. Alas, the genre of mridangam makers has come down with time. Mr. Johnson, an expert maker, with a hoary family tradition of mridangam making is one of the handful experts left.
Therefore scientific analysis and standardization become useful for future. This is precisely why the efforts of Drs. Ramasami and Naresh, collaborating with Sri Sivaraman (and Johnson, and CLRI retirees Kalaivasu, V Arumugam and R Sanjeevi) become important.
FFT analysis of the sounds from the patch and the skin showed that the “Dheem” stroke (the fundamental), for example, is 146 Hertz in frequency.
The second harmonic or “chapu” occurs at 275 nm, the third “Num/Mectu” is 410 Hz. Note that Dheem 146 Hz is actually 1.07 times that of the fundamental for a 24 inch resonator, showing the effect of the black patch.
Likewise, the ratio of Dheem to Chapu is not 0.5 but 0.535. Then again, how long does a given sound take to ‘decay' or fall silent? This “sound to silence” too depends on the patch and on the way the player hits. Sri Sivaraman's “Arechappu” or half hit (on the side of the skin with almost horizontal hand) generates sounds at the 2nd, 4th and 8th harmonics (275, 550 and 1100 Hz). Some dexterity of hand!
Scientific analysis of this kind is not just fun or explanatory. It goes to help the artisan or the instrument maker with standardized data. Ramasami has remarked: “the culture of science is to measure, discover, standardize and calibrate.
The culture of art is to feel, create, differentiate and set standards.
With such a meeting of science and art, one could try and discover to create, feel to measure, differentiate to standardize and set standards to calibrate. Here then is where the cultures meet and ensure that the future is a continuum of the past through the present. dbala@lvpei.org
