I had an interesting experience this weekend... I visited some southern Indian friends of mine from college, one of whom plays tabla and, in fact, was my original inspiration to play. In talking to him, I learned that he never received any training whatsoever (not even the book and videotape approach I'm using). He had a general familiarity with Indian classical music and just... played based on that. I always thought he was very good, and he plays for divali gatherings in Chicago, etc. In watching him play, though, I did notice his hands were positioned quite differently from what I've seen in books; I also noticed he never seems to play certain bols like Dhira Dhira. He's been playing like this for 30 years, and now that he's retired, says he plans to go to India to take some formal teaching from a guru. I'm curious to find out whether a guru would tell someone like this that they are "doing everything wrong". I mean... I guess if you get a good sound that you and other people enjoy, then there isn't really any WRONG technique... it's just "George-uncle gharana".
One other recollection... this guy's brother also plays... I remember when they used to both play together, they would look straight at each other... moving and playing together as if some unspoken language was passing between them. It was like magic!
This is quite common. In fact I have no doubt that tabla originally started this way. Being from Pakistan myself, I have know a ton of people who play a mean tabla. Many Afghani friends of mine also play well with no training at all. You have to understand that this type of playing is very different then "classical Indian/Pakistani" tabla playing. Its like going into some parts of the deep south. You may find some guys who play a mean fiddle but by no means are they a ITZHAK PERLMAN!
It's the folk tradition, versus the classical tradition. It's the same instrument, but in a totally different musical setting.
Just like in the West, you can learn classical piano, jazz piano, pop piano, or just mess around on the piano when you visit your friend who has a piano... You get the idea.
Depending on what kind of music you like, you can approach the instrument in a different way. However, it is commonly accepted that if you learn tabla in the Indian classical tradition, playing anything else is no problem.