is principally based on melody and rhythm, not on harmony or counterpoint. Its origin is in Vedic Hymns of the Hindu Temple, so the roots are religious. The tradition is an oral one, it is taught directly by the Guru. The heart of Indian music is the Raga: the melodic form upon which the musician improvises. The traditional performance begins with the Alap. After this slow beginning the musician moves onto Jor, where rhythm enters. There is no drum in either of these sections. Then the Gat is evolved, which is the fixed composition of the Raga. Drums enter, and this section becomes the vehicle for the musician to return to after improvising - which he can do within the format of the Raga and Tala, its time cycle. The music becomes more playful and exciting with the development of the dialogue between the tabla and the main instrument. The classical music of the India-Pakistan-Bangladesh subcontinent (in short Indian classical music) is one of the few ancient art forms still widely practised today. In recent years it has been much appreciated all over the world. There are many different styles but the two major ones are the Hindustani from the north and the Karnatic style from the south. Indian instruments are very delicate, affected by humidity and spotlights among other things and they need to be tuned and re-tuned before and also during the performance. This forms part of the concert and first-timers to an Indian Classical Concert are often amazed by this.
Glossary
Alap In certain styles, the beginning of a musical composition. It is given the highest place in Indian music. The Alap expresses and then unfolds the characteristics of a Raga in respect of melody (Phrases, important notes, tone range, etc.) It has no measured rhythm, and is very slow in tempo.
Choottaan A taan, musical figure,that has upward and downward movements at great speed. Bhava Mood, feelings.
Dadra Tala of six beats, drut laya, fast tempo.
Javaab Saugat, the section in which the percussion instrument very closely follows and imitates the main instrument.
Tala Time measure. Every tala has a set number of beats divided up into bars.
Gharana From ghar, meaning home. In musical terms it means school of family. Various gharanas of music and dance were established by famous Artists and teachers. Every gharana has to this day, it's distinctive styles and conventions.
Gat or Gath Usually the fourth and final section of an instrumental performance. Gath are structured compositions, although allowing for improvisation. They end as it were, in a tornado of rhythm. Guru Spiritual mentor, teacher. Jhala follows Jor, It is characterised by increasing speed and excitement, ending with a climax. The two side strings (rhythm or drone strings) are played with very fast action of the pick worn on the right index finger. Jor or Jorh the second part of the solo exposition of the Raga, and the part into which an instrument Alap leads. It begins with the added element of rhythm, which, combining with the weaving of innumerable melody patterns, gradually gains in tempo and brings the Raga to the final movement.
Laya Tempo, larrant, the rhythmic composition between the percussion and the stringed instrument.
Matra A Beat
Raga A combination of notes, aesthetically pleasing.
Sampurna ragas use all seven notes.
Savaal Savaal-Javaab, question -answer session between the main instrument and the percussion instrument.
Sum The most important beat in a tala.
Vadi Dominant note of a raga.
Hindustani Music the classical music of north India. The music of Pakistan, Bangladesh and Afghanistan is essentially the same as that of north India.

There is also an excellent description of Indian Classical Music at
Ken Zuckerman’s Home Page (see links)