I wrote the following some time ago in response to someone who had asked similar questions about the use of the theremin in Indian music.
*********************************
As a serious student of classical Northern Indian music (surbahar and rudra vina) for more than 40 years, and as a student of the theremin for the last ten years, I would like to explain exactly why I believe it is not possible to play Indian raga on the theremin.
First of all, there is the matter of vibrato.
Precision theremin cannot be played without vibrato because it is vibrato that gives the thereminist the leeway to constantly adjust or “trim” the pitch of the instrument as he or she plays.
Classical Indian music, on the other hand, does not use vibrato at all because it is a quarter tone system in which the octave (or ‘saptaka’) has twenty-two “srutis” or microtones. If you play vibrato in Indian music, you are actually encroaching on the adjacent note. (I should perhaps add that modern “Bollywood” pop, which is highly westernized, does use vibrato).
Indian music has evolved over millennia along with the instruments that are used to play it, so the instruments and the music are perfectly suited to one another. When western instruments are introduced, such as the guitar or the violin (which was probably introduced by the Portuguese over 300 years ago) the playing techniques must be adapted to the Indian musical idiom. Vishwa Mohan Bhatt has successfully adapted the guitar to Indian raga but in order to do that he had to modify it, creating an entirely new instrument called the “mohan vina”.
Some instruments, like the harmonium (which was introduced by the English in the 18th century) have never really fitted Indian music but have remained popular in India in spite of that. Just as a historical footnote, the harmonium was banned from use on All India Radio following independence in 1947. Curiously, only a decade earlier, the Third Reich in Germany had banned the use of the harmonium’s cousin, the accordion.
Indian music requires a far greater degree of precision pitch control than it is possible to acquire on the theremin. People often think that because the theremin can play “meend” (a slide from one note to another) that it ought to be able to play Indian raga but this is a result of a lack of familiarity with the theremin and its limitations. There are many Indian musical ornaments and embellishments, such as fast “tans” (rapid successions of defined notes) that it is not possible to play at all on a theremin.
We thereminists have enough problems trying to stay in tune in a 12 tone system, without having to worry about a system in which there are 22 tones.