Like North Indian music, Carnatic or South Indian music is also underwritten by raga (melodic structure) and tala (rhythmic cycle). Although improvisation plays an important role, compositional vocal music remains the dominant form. Even where the recital is purely instrumental, the music is nearly always drawn from the vocal repertoire, largely featuring the songs of the 18th century 'Holy Trinity' of composers Thyagaraja, Muthuswami Dikshithar and Shyama Shastri. The lyrics, in various languages, including Tamil, usually have devotional themes and are often also part of the classical dance repertoire.

A genre known as kriti (an extended song composition in 3 parts) is the focal point of Carnatic music. A kriti is generally based on one raga but where there are several ragas in the same composition, it is known as a ragamalika or ‘garland of ragas.’ Kritis are made up of a pallavi (similar to a refrain in Western music), drawn from one or two of the opening lines, followed by an anupallavai (an optional second verse) and finally the charanam (the longest verse which concludes the song recital and, in its final lines, contains the poet-composer’s musical hallmark or signature.)

Other genres requiring considerable improvisation and collectively known as kalpana sangeetham ('music of the imagination') are equally predominant. Among these, alapana, also known as ragam, is a pulse-free opening section in which a raga is slowly explored and revealed, before launching into the composed song which is based on the same raga. Depending on the performer’s ability, this section can last anything from 15 to 45 minutes. Performers and instrumental accompanists often perform the alapana together as well as individually and in turn, with the vocalist's phrases often being shadowed by that of a violin, flute or harmonium.

The vocal genre known as varnam is usually performed at the beginning of a recital and consists of very basic, simple lyrics which are used to explore the entire range of a raga. In Sanskrit varna means ‘colour,’ hence the performer attempts to gradually reveal the many hues and characteristics of the raga.

Another important vocal genre is niraval, improvisation of usually just one selected line from a kriti song, but it makes huge demands on a performer’s imagination and creativity in that every variant of the improvisation must sit comfortably within the given rhythm cycle whilst exploring every possible nuance of the raga. Usually only performed by seasoned artists who know that the success of a niraval also depends on choosing an appropriate line from the kriti, i.e, one that contains numerous layers of meaning.

A vocal form known as kalpanaswaram is a basic kind of melodic improvisation within a specific rhythm cycle and is usually sung at the end of a song, using only the syllables of the scale tones - Sa, Ri, Ga, Ma, Pa, Dha, Ni.

A three-part genre called ragam tanam pallavi, often referred to as RTP, is one in which an exploratory raga introduction is followed by the performer extending the raga through tanam. This section has very strong associations with the veena (instrumental) tradition and specific syllables in particular combinations are sung at this stage. Even though there is no percussion, a distinct rhythmic pulse is discernible.

Finally, for the pallavi part, the singer is joined by the percussionist to begin some very complex and intricate melodic and rhythmic phrases for which the tempo is gradually increased. A thillana, a short rhythmic piece, similar to the tarana of North Indian music, is often sung to conclude a concert.

• Listen to the music | Aruna Sairam leads a 5-piece Carnatic group through the ominous Raga Shanmukhapriya, often associated with warlike deities such as Murugan and Shiva. Live from Darbar Festival 2009:

• Jameela Siddiqi is an author, linguist, and BBC cultural commentator, specialising in postcolonial fiction and the devotional music of South Asia

Darbar Arts & Heritage believes in the power of Indian classical music to stir, thrill, and inspire. To find out more, get the Darbar newsletter, explore our YouTube channel, or sign up to the Darbar Concert Hall to watch extended festival performances in pristine HD quality.