The Fundamental Components of Hindustani Music
There are three main components to the classical music of India - Drone, Raga, and Tala.
Unlike western music's, Indian music is not based on harmony. The harmonic principle of contrast between simultaneous sounds is foreign to the Indian conception of music. The concept of modulating (or changing) keys is also absent. Instead, the music is based on a drone, a continual pitch that sounds throughout the concert. This acts as a point of reference for everything that follows, a home base that the musician returns to after a flight of improvisation.
Raga - Organization of Melody
"Raga" is one of those troublesome words which has no equivalent in English, and is thus difficult to define. Terms like "generalized melody" or "melodic framework" are perhaps the best English descriptions, although they are only somewhat helpful.
I like to describe a raga as being about halfway between a scale and a tune. A scale is just a set of notes, which can be used in any way you want. A tune leaves no room for spontaneous creation of melody. A raga lacks the total freedom of a scale, but has much more freedom than a tune.
A raga may be characterized in a number of ways. It is built out of a specific selection of tones from the octave (at least five), like a scale. But in a scale all notes are equal. A Raga will have notes of greater and lesser significance. A raga will also have characteristic phrases that are used in its performance, and specific ways in which the notes cannot be used. Each raga is also associated to a particular mood, and to a particular time of day or season of the year.
The result is a melodic structure that is easily recognizable, yet infinitely variable. No two performances of the same raga, even two performances by the same musician, will be identical. Indeed the same raga may be played by the same musician one night for half an hour, the next night for an hour and a half. Yet the character of the raga, the mood it creates, will still be the same.
Tala - Organization of Rhythm
In the same way that ragas are melodic structures, talas are rhythmic structures. A tala can be thought of as a cycle, divided into equal beats which are collected into subgroups. So, for example, Rupak tala consists of seven beats, a group of three beats followed by two groups of two beats (sometimes represented 3+2+2).
The tala is usually represented by a series of strokes (called "bols") on the tabla, reflecting the sub-groupings within the tala. The tabla player will vary the strokes that he plays, but will do so in a manner consistent with the basic rhythm of the tala. In particular, he will be careful to differentiate between the tali (on-beats) and khali (off-beats), which are defined for each tala.
The most important beat of the tala is the first one, called "sam". In performance, the soloist may go off on a long improvised phrase that may last for many cycles of the tala, but will always return to the composition on the sam.