I failed to find a piece of classical indian music that modulates from a chord to another one. Can anyone give a example of not "mono chord" indian music, and if not possible, is there a reason for this?
Indian Classical music we usually don't have a chord system. There is usually a drone (mono chord) playing in the background through a stringed instrument assisted by the
flute etc in the foreground. Music is based on a
Raga and various forms which are played over the drone in the background.
Majorly two drones are used :
1) सा (C) , प (G)
2) सा(C) , म(F)
The reason for this may be the answer to the question - Why do some painters choose a plain background for their art over a coloured background?
As of today, most of the film industry music in India is the fusion of the two - pure
Classical Indian and the
Western Chord system.
In classical music, there is a rare practice called Murchana or graha bheda or shruti bheda, which changes the tonic, but all the notes of the base raga remain the same. As a result the raga sounds different. In light music, the tonic key may change, but the raga remains the same. In the second category, the chords will change, try this out:
To answer your question (in a non fusion context) both traditions of ICM do not have western harmony (i.e. motion of chords from one to other either in a functional or non functional sense).
We do have drones though. A drone fixes reference pitches against which a performer sings/plays their instrument.
The most common drone configuration is 5-8-8-1 (perfect fifth, two octaves, tonic). For the ragas that do not have the perfect fifth you can also use 4-8-8-1 (perfect 4th instead of 5th).
Note there is no harmonic motion in a drone. Its literally these notes played over and over.