Instrumental or vocal ensemble
In general, 'trio' denotes a group of three solo instruments or voices (Randel 2003). The term is also used to describe a composition for such a group. The most common types of such compositions are the "piano trio" — piano, violin and cello — and the "string trio" — violin, viola and cello (Schwandt 2001). In vocal music, the term 'terzet' is sometimes preferred to 'trio' (McClymonds, Cook, and Budden 1992).
From the 17th century onward the word 'trio' is used to describe a contrasting second or middle dance appearing between two statements of a principal dance, such as a minuet or bourée. This second dance was originally called a 'trio' from the 17th-century practice of scoring it for three instruments, for example two oboes and bassoon. Later examples continued to be referred to as trios, even when they involved a larger number of parts (Randel 2003; Schwandt 2001).
In the 18th century, the term ‘trio’ also was used to describe any instrumental composition for three unaccompanied musical strands, regardless of the number of instruments actually involved. Trios for a single keyboard instrument are found in the music of Johann Sebastian Bach, for example his organ trios, BWV 525–30, and three-part inventions, or Sinfonias, BWV 787–801 (Schwandt 2001).
'Trio' also occurs in the name for the musical form trio sonata, which was popular in the 17th and early 18th centuries. A trio sonata is written for two solo melodic instruments and basso continuo, making three parts in all, hence the name trio sonata. However, because the basso continuo is usually made up of at least two instruments (typically a cello or bass viol and a keyboard instrument such as the harpsichord), performances of trio sonatas typically involve at least four musicians.
Contemporary music group/band
In rock music, bands most typically have four to five members, but there are also many three-person bands. The archetype of the trio in rock music is the power trio, having a guitar, bass, and drums, with one or more of those performers also singing. Notable examples of trios following this pattern include Rush, The Police, Motörhead and Nirvana. However there are other variations, for example Emerson, Lake & Palmer, where the guitar is replaced by a keyboard. Operating as a trio allows the musicians involved to showcase their skills, as they are collectively carrying the burden of not having the typical fourth member. Jimi Hendrix, although often remembered as a soloist, often performed as part of a trio.
A trio may also rely on a combination of instrumentation and vocal harmonization. Crosby, Stills, & Nash began as a trio noted for their vocal congruence. Some trios rely entirely on the singing skills of the performers working in front of pre-recorded instrumental tracks. These include groups like Destiny's Child and TLC. In rap music, a trio may be composed of three performers who alternate vocal parts, as with The Beastie Boys, The Lonely Island, and Foreign Beggars, or may be two vocalists along with a DJ who provides the instrumentation through sampling and turntablism, as with Salt-N-Pepa, composed of two vocalists and DJ Spinderella.
Common forms of trio include:
- Clarinet-cello-piano trio (clarinet, violoncello, piano)
- Clarinet-viola-piano trio (clarinet, viola, piano)
- Clarinet-violin-piano trio (clarinet, violin, piano)
- Flute, viola and harp (flute, viola, harp)
- Harmonica trio (chromatic harmonica, bass harmonica, chord harmonica)
- Horn trio (horn, violin, and piano)
- Jazz trio (piano, bass, drum kit)
- Organ trio (Hammond organ, drummer, jazz guitarist or a saxophone)
- Piano trio (violin, cello, piano)
- Power trio (electric guitar, bass guitar, drum kit)
- String trio (violin, viola, cello)
- Trio sonata (two instruments plus continuo)
- McClymonds, Marita P., Elisabeth Cook, and Julian Budden. 1992. "Trio [terzet]". The New Grove Dictionary of Opera, 4 vols., edited by Stanley Sadie. London: Macmillan Press Limited. ISBN 9780935859928; ISBN 9780333485521; ISBN 9780333734322; ISBN 9781561592289.
- Randel, Don Michael. 2003. The Harvard Dictionary of Music, fourth edition (Harvard University Press Reference Library). Cambridge: Belknap Press of Harvard University Press. ISBN 978-0674011632.
- Schwandt, Erich. 2001. "Trio". The New Grove Dictionary of Music and Musicians, second edition, edited by Stanley Sadie and John Tyrrell. London: Macmillan Publishers.