In the 12th and 13th centuries, Muslim conquests throughout India divided Indian classical music into two systems that persist today, north (Hindustani) and south (Carnatic). In South India the raga—"the collection of pitches a performer may use in a piece—is more closely connected to worship. In both systems the performer tries to make the raga "characteristic of the emotion it seeks to establish" through improvisation—and with the "72 basic scales and more than 500 derived forms" that are available within the South Indian raga system, the performer has a wealth of options. Liner notes include an overview of the South Indian musical system; descriptions of traditional instruments such as the gottuvuadyam, mridugam, and tambura; track notes with notated musical analysis; and pictures of the performers and instruments.