The music of India sounds quite exotic to most Western audiences. Two major reasons for this are the differences between the two traditions in tuning and scales. The following is a very basic introduction to these differences, meant for someone who has a basic understanding of Western music theory but no knowledge of the Indian music tradition. For an introduction that concentrates on music appreciation and avoids music theory, please see Listening to Indian Classical Music. (For more about Western scales and tuning, please see Major Keys and Scales, Minor Keys and Scales, and Tuning Systems.) I believe the terms used here are from the Northern Indian (Hindustani) tradition. The Southern Indian (Karnatic) tradition, uses some different terms, but the fundamental ideas are the same.

One reason that Indian music sounds so different to the Westerner is that the major/minor tonal system is not used. Harmony, and specifically the major/minor tonal system, has been the basic organizing principle in Western music - classical, folk, and popular - for centuries. In this system, a piece of music is in a certain key, which means it uses the notes of a particular major or minor scale. The harmonies developed using those notes are an integral, basic part of the development and form of the music. Most of the complexity of Western music lies in its harmonies and counterpoint.

The music of India does not emphasize harmony and does not feature counterpoint. In fact, most Indian classical music features a single melody instrument (or voice) accompanied by drone and percussion. There is no counterpoint and no chord progression at all. Instead, the interest and complexity of this music lies in its melodies and its rhythms. (Just as Indian music can seem confusing to someone accustomed to listening for harmonic progressions, Western melodies, based on only two types of scales, and Western rhythms, based on only a few popular meters, may sound overly similar and repetitive to someone accustomed to Indian music.)

Western music divides an octave into the twelve notes of the chromatic scale. But most pieces of music mainly use only seven of these notes, the seven notes of the major or minor key that the piece is in. Indian music also has an octave divided into twelve notes. These twelve notes are called swaras; they are not tuned like the notes of the chromatic scale (please see below). Also similarly to Western music, only seven notes are available for any given piece of music.

But there are important differences, too. Western scales come in only two different "flavors": major and minor. The two are quite different from each other, but any major key sounds pretty much like any other major key, and any minor key sounds basically like every other minor key. This is because the relationships between the various notes of the scale are the same in every major key, and a different set of relationships governs the notes of every minor key. (Please see Major Keys and Scales and Beginning Harmonic Analysis for more on this.)

The seven-note thats of Indian music, on the other hand, come in many different "flavors". The interval pattern varies from one that to the next, and so the relationships between the notes are also different. There are ten popular thats in North Indian music, and many more in South Indian.

Making for even more variety, a piece of Indian classical music may not even use all seven of the notes in the that. The music will be in a particular raga, which may use five, six, or all seven of the notes in the that. And a that can generate more than just three ragas (one pentatonic, one hexatonic, and one full raga). Kalavati raga (C, E flat, G, A, and B flat) and Shivranjani raga (C, D, E flat, G, and A), for example, are two different pentatonic ragas derived from Kafi that. Thus there are hundreds of ragas available, and a competent Indian musician is expected to be able to improvise in many of them.

Furthermore, the raga is not just a collection of the notes that are allowed to be played in a piece of music. There are also rules for how the notes may be used; for example, the notes used in an ascending scale may be different from the notes in a descending scale. And the raga may even affect the tuning of the piece.

The tuning of modern Western Music is based on equal temperament; the octave is divided into twelve equally spaced pitches. But this is not the only possible tuning system. Many other music traditions around the world use different tuning systems, and Western music in the past also used systems other than equal temperament. Medieval European music, for example, used just intonation, which is based on a pure perfect fifth. (Please see Tuning Systems for more about this.)

The preferred tuning system of a culture seems to depend in part on other aspects of that culture's music; its texture, scales, melodies, harmonies, and even its most common musical instruments. For example, just intonation worked very well for medieval chant, which avoided thirds, emphasized fifths, and featured voices and instruments capable of small, quick adjustments in tuning. But equal temperament works much better for the keyboard instruments, triadic harmonies, and quick modulations so common in modern Western music.

In India, the most common accompaniment instrument (as ubiquitous as pianos in Western music) is the tanpura. (There are several alternative spellings for this name in English, including taanpura and tambura.) This instrument is a chordophone in the lute family. It has four very long strings. The strings are softly plucked, one after the other. It takes about five seconds to go through the four-string cycle, and the cycle is repeated continuously throughout the music. The long strings continue to vibrate for several seconds after being plucked, and the harmonics of the strings interact with each other in complex ways throughout the cycle. The effect for the listener is not of individually-plucked strings. It is more of a shimmering and buzzing drone that is constant in pitch but varying in timbre.

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 thats. 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 higher. 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 shrutis; the minor whole tone between D and E would be 3 shrutis.

In some ragas, 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 divided into 22 shrutis. This is only for tuning, however; for any given that or raga, only twelve specifically-tuned notes are available. The 22 shrutis each have a specific designation, and the intervals between them are not equal; the frequency ratios between adjacent shrutis ranges from about 1.01 to about 1.04.

In spite of the fact that these tunings are based on the physics of the harmonic series, Indian music can sound oddly out of tune to someone accustomed to equal temperament, and even trained Western musicians may have trouble developing an ear for Indian tunings. As of this writing, one site devoted to helping Western listeners properly hear Indian tunings was The Perfect Third.

As mentioned above, Indian music, like Western music, recognizes seven notes that can be sharped or flatted to get twelve notes within each octave. A flatted note is called komal. A sharped note is called teevra.