Musical improvisation is the creation of spontaneous music, often within (or based on) a pre-existing harmonic framework or chord progression. Improvisers use the notes of the chord, various scales that are associated with each chord, and chromatic ornaments and passing tones which may be neither chord tones not from the typical scales associated with a chord. Musical improvisation can be done 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.