Term referring to the spontaneous performance of music without previous preparation or any written notes. Improvisation can be seen in music of the Medieval era, where singers were trained to improvise additional lines to liturgical chant while it was being performed, in the Renaissance, where a musician would improvise over the written chords usually on a keyboard instrument or on a viol, in the Baroque, where ornamentation and realization of figured bass was common, in the Classical and Romantic eras, where cadenzas of concertos were expected to be improvised, and in 20th century jazz. performance that involves invention while playing. Improvisation can either be guided by pre-existent material (loosely based on a particular melody, for instance), or be free of such influences. music played spontaneously, alone, or against a pre-arranged background of chords and melodies. Liszt and Chopin were renowned for the improvisations. today, they are common in organ recitals and in jazz music