The Prelude Op. 28, No. 15, by Frédéric Chopin is known as the "Raindrop" prelude. It is one of the 24 Chopin preludes. This is the longest of the preludes. It lasts between five and seven minutes. The prelude is famous for its repeating A-flat. This note appears throughout the piece. It sounds like raindrops to many listeners. It is known for it's repetitive raindrop motif.