Carnatic music is one of the oldest forms of music in the world. Combining emotion and the spirit of improvisation, it contains a strong scientific approach. This is mainly due to the contributions of such inspired artists as Purandara Dasa, also known as the Grand Father of Carnatic Music, and other scholars who have codified the system and gave it a clear format as a medium of teaching, performing, prayer and therapy.
The basis of Carnatic Music (and Hindusthani Music) is Ragas (melodic scales) and Talas (rythmic cycles). There are seven rhythmic cycles and 72 fundamental ragas. All other ragas are considered to have stemmed from these. An elaborate scheme exists for identifying these scales, known as the 72 Melakarta Ragas.
Carnatic music abounds in structured compositions in the different ragas. These are songs composed by great artists and handed down through generations of disciples. While the improvised elaboration of a raga varies from musician to musician, the structured portion is set. These compositions are extremely popular, with a strong accent on rhythm and lively melodic patterns. Three saint composers of the nineteenth century, Tyagaraja, Muthuswami Dikshitar and Shyama Shastri, have composed thousands of songs that remain favourites among musicians and audiences.
An important element of Carnatic music is its devotional content. The lyrics of the traditional compositions, whether mythological or social in nature, are set entirely against a devotional or philosophical background.
Carnatic Music differs from western music in a lot of ways. One of the main differences is that while Western Music has absolute notes, indian music is based on relative notes in order to cater for singers with differing "natural" pitches.
Here are some interesting and very educational Links on Carnatic Music.