That sounds like a good Arduino project!
The air solenoids will need more voltage & current than you get direcly from the Arduino. You'll probably need MOSFET for each solenoid. I assume they run off 12V. Can you find out how much current they take? Or, do you have a multimeter to measure the current?
I have downloaded the scores from these tunes and it looks like you can do them all with 6 different tuned horns.
As long as they are tuned to the correct note/pitch...
Doesn't traditional indian music use a different musical scale than Western music? The Western scale has 12 notes per octave. But most songs don't use all of the notes, and you can sometimes transpose (shift up or down) to allow a particular instrument with limited notes to play a song. Ane of course, some songs span more than one octave. But in this kind of application you should be able to "fake it" and play the note in the octave you happen to have.
Another small detail. With automobile horns, sometimes there is a fraction of a second delay. So, you might have to build some "overlap" into the timing. That is, start the 2nd note slightly before the 1st note ends.