In olden times, many ustads and pandits used to do candlelight practice, also known as jyoti riyaaz.
Two major concepts should be kept in mind when doing candlelight practice:
1) you must play one composition until the candle burns out
2) you must stare into the flame jyoti while practicing
Candlelight practice should not be done in a very fast speed. It is better to take a taal versus a particular composition (ie. teentaal or jhaptaal theka versus a kayda).
It is also very important to have the taanpura drone and perfectly tuned tabla during candlelight practice.
Fire has four basic elements: heat, sound, light and darkness. This is why fire is worshiped in traditions around the world.
Staring into the fire is called tratak. When playing a theka and doing this, after some time (after weeks in fact), one feels that the taal and the flame elements begin to merge and drive one into unknown areas. Its a kind of experience that cannot be described in words.
Sometimes one feels that the sound of the theka disappears and reappears. Sometimes one feels that the flame appears and disappears. Sometimes one feels that both disappears and reappears. That is the time when you meet total emptiness – the gap where all secrets reside.
I strongly recommend that anyone who has the mood to go for any experience of music, but do this practice. You will not be disappointed.