The role of tambura spectra in drone tunings of North Indian ragas
Edward C. Carterette, Nazir Ali Jairazbhoy, Kathryn Vaughn · The Journal of the Acoustical Society of America · 1988
As part of a program on the role of drone interactions with North Indian ragas played on the sitar, the waveforms of the tambura for the most common drone tuning of the four strings [pa, sa1, sa2, sa′ (low sa)] were analyzed. Each of the strings was played with and without juari threads that have the effect of separating the string slightly from the bridge. The resulting sound is referred to by Indian musicians as a buzz. Without juari the pitch heard is very close to the string fundamental and the partials fall linearly in decibels. With juari the pitch is heard at one or even two octaves above the base pitch and the partials have great power as far as the 20th partial. With juari the 4th, 7th, 11th, or 12th, and the 17th partials have more amplitude than the fundamental. Total harmonic distortion is on the order of 1 to 19 dB without juari but ranges from 12 to 44 dB with juari. The upward spread of energy into higher partials imparts richness to tambura tones, and underlies the use of different drone tunings for different ragas. The pitch and timbre changes with tambura are discussed in terms of the psychoacoustics of complex tones.