Each "rāga" provides the musician with a musical framework within which to improvise. The specific notes within a "rāga" can be reordered and improvised by the musician. "Rāga"s range from small "rāga"s like Bahar and Shahana that are not much more than songs to big "rāga"s like Malkauns, Darbari and Yaman, which have great scope for improvisation and for which performances can last over an hour. "Rāga"s may change over time, with an example being Marwa, the primary development of which has gone down to the lower octave compared to the traditionally middle octave. Each "rāga" traditionally has an emotional significance and symbolic associations such as with season, time and mood. The "rāga" is considered a means in Indian musical tradition to evoke certain feelings in an audience. Hundreds of "rāga" are recognized in the classical tradition, of which about 30 are common. Each "rāga", state Dorothea E. Hast and others, has its "own unique melodic personality".