Musical improvisation is the creation of spontaneous music, often within (or based on) a pre-existing harmonic framework or chord progression. Improvisation is the act of instantaneous composition by performers, where compositional techniques are employed with or without preparation. Improvisation is a major part of some types of music, such as blues, jazz, and jazz fusion, in which instrumental performers improvise solos, melody lines and accompaniment parts. In the Western art music tradition, improvisation was an important skill during the Baroque era and during the Classical era. In the Baroque era, performers improvised ornaments and basso continuo keyboard players improvised chord voicings based on figured bass notation.