FANTASIA, in Music, an Italian term which means either a composition improvised upon the organ, or piano-forte, or violin, &c., according to the free fancy of the performer, and not elaborated according to any strict rules or forms of construction, while still subject to the fundamental laws of melody, modulation, and harmony;—or, a written composition in which the musician indulges his fancy unrestrained by conventional forms of developed themes and movements, but yet bestows more careful attention upon details than is required in the improvised fantasia. One of the finest specimens of a written fantasia is Mozart's in C minor, No. 24 of the list of his works published in 1805 by J. André of Offenbach. The "Fancies" of Bird, Bull, and other old English musicians of the sixteenth century, were dry and difficult compositions for a keyed-instrument, worked out upon popular airs. (G. F. G.)