A prelude (German: Präludium or Vorspiel; Latin: praeludium; French: prélude; Italian: preludio) is a short piece of music, the form of which may vary from piece to piece.[1][2] The prelude may be thought of as a preface. While, during the Baroque era, for example, it may have served as an introduction to succeeding movements of a work that were usually longer and more complex, it may also have been a stand-alone piece of work during the Romantic era. It generally features a small number of rhythmic and melodic motifs that recur through the piece. Stylistically, the prelude is improvisatory in nature. The prelude also may refer to an overture, particularly to those seen in an opera or an oratorio.

The first preludes to be notated were organ pieces that were played to introduce church music, the earliest surviving examples being five brief praeambula in the Ileborgh Tablature of 1448.[3] These were closely followed by freely composed preludes in an extemporary style for the lute and other Renaissance string instruments, which were originally used for warming up the fingers and checking the instrument's tuning and sound quality, as in a group of pieces by Joan Ambrosio Dalza published in 1508 under the heading tastar de corde (in Italian, literally, "testing of the strings").[3][4]

Keyboard preludes started appearing in the 17th century in France: unmeasured preludes, in which the duration of each note is left to the performer, were used as introductory movements in harpsichord suites. Louis Couperin (c.1626–1661) was the first composer to embrace the genre, and harpsichord preludes were used until the first half of the 18th century by numerous composers including Jean-Henri d'Anglebert (1629–1691), Élisabeth Jacquet de la Guerre (1665–1729), François Couperin (1668–1733) and Jean-Philippe Rameau (1683–1764), whose very first printed piece (1706) was in this form. The last unmeasured preludes for harpsichord date from the 1720s.

The development of the prelude in 17th century Germany led to a sectional form similar to keyboard toccatas by Johann Jakob Froberger or Girolamo Frescobaldi. Preludes by northern German composers such as Dieterich Buxtehude (c.1637–1707) and Nikolaus Bruhns (c.1665–1697) combined sections of free improvised passages with parts in strict contrapuntal writing (usually brief fugues). Outside Germany, Abraham van den Kerckhoven (c.1618–c.1701), one of the most important Dutch composers of the period, used this model for some of his preludes. Southern and central German composers did not follow the sectional model and their preludes remained improvisational in character with little or no strict counterpoint.

During the second half of the 17th century, German composers started pairing preludes (or sometimes toccatas) with fugues in the same key; Johann Pachelbel (c.1653–1706) was one of the first to do so, although Johann Sebastian Bach's (1685–1750) "prelude and fugue" pieces are much more numerous and well-known today. Bach's organ preludes are quite diverse, drawing on both southern and northern German influences. Most of Bach's preludes were written in the theme and variation form, using the same theme motif with imitation, inversion, modulation, or retrograde the theme as well as other techniques involved in this baroque form.