The black tuning patch at the head's center — why the drum rings at a definite pitch.
The circular black patch built from a paste of iron particles, starch, and gum, applied in thin layers and polished until it cracks into a fine mosaic. Its mass loads the membrane so the overtones align harmonically — the reason the dayan sounds a clear, tunable note instead of a thud.
On the bayan the syahi sits off-center, leaving bare skin for the heel of the hand to press and bend the pitch. The patch is fragile craft: flaking edges or a dulled ring usually mean the pudi is due for replacement, not repair.
Further reading
C. V. Raman, "The Indian Musical Drums," Proceedings of the Indian Academy of Sciences, Section A, Vol. 1 (1934).
Rebecca Stewart, The Tabla in Perspective (PhD dissertation, University of California, Los Angeles, 1974).
