A prelude is a short composition with a small number of melodic and rhythmic motif and whose structure can vary greatly from piece to piece. Preludes originated in the Baroque era as a piece that was played as an introduction to another, longer work, often similar to an overture for an opera or oratorio. However, they broadened to include standalone pieces during the Romantic era and became a popular form of composition, not only for orchestras but also for solo pianos. Preludes have been written by many of the greatest and best-known composers, including Bach, Chopin, Debussy and Rachmaninoff.