The term "impromptu" suggests that a piece has a casual, offhand quality—perhaps that it's even being improvised on the spot. Sometimes, though, it's just a handy term for a short, stand-alone piece ...
Look out for Schubert's Impromptu No. 3, which contains a nod to one of the world's most famous pop songs... Just after he wrote Fly Me to the Moon, Schubert wrote his Impromptu No. 3. Absolute ...