3.4 Indian classical music: tuning and ragas  (Page 4/5)

And the constant pitches of that drone are usually a pure perfect fifth . You may have noticed in the figure above that C and G are not flatted or sharped in any of that s. Assuming tuning in C (actual tuning varies), two of the strings of the tanpura are tuned to middle C , and one to the C an octave lower. The remaining string is usually tuned to a G (the perfect fifth). (If a pentatonic or hexatonic raga does not use the G, this string is tuned instead to an F. The pure perfect interval is still used however, and you may want to note that a perfect fourth is the inversion of a perfect fifth.) So a just intonation system based on the pure fifth between C and G (or the pure fourth between C and F) works well with this type of drone.

Pure intervals, because of their simple harmonic relationships, are very pleasing to the ear, and are used in many music traditions. But it is impossible to divide a pure octave into twelve equally spaced pitches while also keeping the pure fifth. So this brings up the question: where exactly are the remaining pitches? The answer, in Indian music, is: it depends on the raga .

Indian music does divide the octave into twelve swaras , corresponding to the Western chromatic scale. Also, just as only seven of the chromatic notes are available in a major or minor scale, only seven notes are available in each that . But because just intonation is used, these notes are tuned differently from Western scales. For example, in Western music, the interval between C and D is the same (one whole tone ) as the interval between D and E. In Indian tuning, the interval between C and D is larger than the interval between D and E. Using the simpler ratios of the harmonic series , the frequency ratio of the larger interval is about 9/8 (1.125); the ratio of the smaller interval is 10/9 (1.111). (For comparison, an equal temperament whole tone is about 1.122.) Western music theory calls the larger interval a major whole tone and the smaller one a minor whole tone . Indian music theory uses the concept of a shruti , which is an interval smaller than the intervals normally found between notes, similar to the concept of cents in Western music. The major whole tone interval between C and D would be 4 shruti s; the minor whole tone between D and E would be 3 shruti s.

In some raga s, some notes may be flattened or sharpened by one shruti , in order to better suit the mood and effect of that raga . So, for tuning purposes, the octave is typically divided into 22 shruti s. This is only for tuning, however; for any given that or raga , only twelve specifically-tuned notes are available. The 22 shruti s each have a specific designation, and the intervals between them are not equal; the frequency ratios between adjacent shruti s ranges from about 1.01 to about 1.04.

As mentioned above, there is a great variety of traditions in India, and this includes variations in tuning practices. For example, Dhrupad, a very old form of North Indian music, can be considered as dividing the octave into 84 rather than 22 microtones, including unusual variations on the C and G drone pitches which are not based on the pure intervals.