on my tabla there is written on the edge: B, C7
does it mean i have to tune it on this note?
well, if it is like this, it is well tuned, but i think most tablas are tuned higher.
how far can i pitch it up, without splitting the puddi?
Normally, the Sa(fisrt note in scale) in indian music is C#, but this depends mostly on how the other instruments are tuned in a group, if your playing alone, it doesn't relly matter to what it is tuned. The best pitch for a tabla is where it souds best, where you get the most clear tone. I think you can get the pitch higher, but i dont think theres any need, specially if it sounds good allready. why fix something that doest need fixing. :-)
