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I'm not sure if you're asking for 'Raga music', but I'll tell you what I know about that, and what I heard to Ravhi Shankar at a concert I could go, many years ago, when he explained the Indian music and the facts that are involved.

-Indian music is mainly religious.

-They are mostly in the area of "oral tradition" or "oral transmission" (that's why it takes so many years to become a 'sitar' or a 'tabla' performer.)

-They are guided by "moment inspiration" and "religious inspiration" (that's why a tune will sound different at each performance), so it's improvisation.