@CDR I lied when I
said that a good book on Indian classical music was Chaudhuri's
Afternoon Raag. That book is on my to-read shelf. The book I was thinking of was his
The Immortals (New York: Knopf, 2009). Here is the passage about the sound of the tanpura. The point of view is that of a singer and teacher named Shyam Lal: