Syahi
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The syahi, also known as "gaab" or "ank", is the black spot found on each of the drums that make up the set of tablas. It is made of a mixture of flour, water and iron filings. Originally the syahi was a temporary application of flour and water. Over time it evolved into the permanent application.
The syahi functions to load only a portion of the skin. For the right hand dum (dayan), this has the effect of altering the resonance frequency of some lower order vibrational modes more than others. This is one of the reasons that the tabla has a sound which approximates a harmonic spectrum, where most drums are characterized by a strong enharmonic quality. This was first described in the early 20th century by C.V. Raman. The action on the left hand drum is a little different. For the bayan, it serves to simply lower the resonance frequency.
The application of the syahi is very involved. It starts with a base layer of mucilage. Thereafter, numerous paper thin layers of “syahi masala” (flour, water, iron filings and other secret ingredients) are applied and rubbed with a stone. Not all of the layers have the same size. The variable sizes allow a special contour to be produced in the finished application.
The rubbing with the stone is crucial to the creation of the syahi. The material from which the syahi is made is inherently inflexible. If it were simply applied in a single layer and allowed to harden then this inflexibility would not let the drum skin vibrate. The process of rubbing or polishing with the stone creates a tight latticework of cracks which extend down to the very base of the syahi. This lattice of cracks indicate that the syahi is composed of countless small particles which articulate with their neighbor but are not joined together. The ability of the particles to move independently is what gives the finished syahi a modicum of flexibility even though the material from which it is made is inflexible.
