Work for solo pf. comp. by Busoni in 3 versions between 1910 and 1912. Sub‐titled Preludio al Corale ‘Gloria al Signori nei Cieli’ e fuga a quattro soggetti obbligati sopra un frammento di Bach. Arr. for 2 pf., 1921. Adapted for org. by work's dedicatee Wilhelm Middelschulte. Based on Bach's Contrapunctus XVIII from The Art of Fugue, in desire to complete Bach's unfinished fugue. Busoni created 4th subject (Bach having comp. only 3), and added 5th.