One of two sub-categories of Indian Classical Music, Karnatic (South Indian) music is the ancient music of India, undiluted by foreign influences, unlike Hindustani music. In the Karnatic tradition, vocal music is ranked highest. Although improvisation plays an important part, a substantial part of Karnatic vocal music consists of pre-composed songs which can have several verses. These set compositions are also used in the teaching of this style of music. Nearly every performance of a Karnatic music composition is unique in that it embodies elements of the original composer's vision, as well as an individual performing musician's interpretation of that vision. A concert of Karnatic vocal music can include many song forms within the same recital and is usually performed with a small ensemble.