John Constable studied at the Royal Academy of Music with Harold Craxton. His career began at the Royal Opera, Covent Garden, where he worked on the music staff. Since 1984, he has served as the principal harpsichordist for the Academy of St. Martin-in-the-Fields, and the principal pianist for the London Sinfonietta, Britain's leading contemporary music ensemble, since its founding. He has performed as a soloist under the batons of such conductors as Simon Rattle, Hans Werner Henze, David Atherton, and Oliver Knussen. He has performed as continuo harpsichordist for recordings of Mozart operas with Colin Davis, Neville Marriner, Simon Rattle, and Georg Solti. With soprano Lucy Shelton, he gave the world premiere of Elliott Carter's Of Challenge and of Love at the Aldeburgh Festival. Constable has performed recitals at the BBC's New British Music and Lutoslawski weekends at the Barbican and the American Independents Festival at the Queen Elizabeth Hall. In 2000, he was a soloist in the Boulez at 75 Festival and in 2001 at the BBC's Schnittke Festival at the Barbican. In 1998, he performed the Elliott Carter Double Concerto with the London Sinfonietta at the Queen Elizabeth Hall and with the ASKO Ensemble at the Concertgebouw. Constable has made numerous recordings of chamber music and song repertoire for Argo, Decca, EMI, Philips, Deutsche Grammophon, Hänssler, and Capriccio. These include a disc of music for viola and piano with Paul Silverthorne, a selection of Liszt songs with Philip Langridge, a collection of Warlock songs with Adrian Thompson and Christopher Maltman, Fauré and Ravel songs with Felicity Palmer, Haydn Lieder with Dame Janet Baker, and A Spanish Songbook with Jill Gomez. He is a frequent collaborator with Lucy Shelton, with whom he has recorded Messiaen's Harawi and the complete songs of Elliott Carter and Stravinsky. Constable is a professor at the Royal College of Music, London, and a Fellow at the Royal Academy of Music.

The London Sinfonietta is among the leading ensembles in the U.K., devoted largely to contemporary music. The group has a large recording catalog stretching back to the LP era, much of it on major labels.

The London Sinfonietta was formed in 1968 by administrator Nicholas Snowman and conductor David Atherton. Atherton served as music director until 1973, and he remained active with the group after that, conducting it on early recordings, including a 1980 release of Michael Tippett's opera King Priam. The orchestra has a core of 11 Principal Players, augmented each year by guest performers as needed according to the repertory being performed. The group has commissioned more than 450 new works and given world premieres of hundreds of others. The orchestra's programming is eclectic; it has programmed works by such composers as Luciano Berio, Harrison Birtwistle, Steve Reich, and Karlheinz Stockhausen, and it has also performed mainstream repertory, including Bach, Britten, and Stravinsky, and even jazz pieces and works of musical theater. The London Sinfonietta has an artistic director; since 2007, it has been Andrew Burke. It is also often led by guest conductors, which include Markus Stenz and composer Oliver Knussen, among others. Knussen also served as artistic director from 1998 to 2002.

The London Sinfonietta has London's Southbank Centre as its home base, performing several concerts there annually, including an annual concert for schools. The group also appears at other British venues and has toured regularly across Europe, the Americas, and Asia. It has developed novel methods of communicating its work digitally, including a Clapping Music mobile phone game app based on Reich's work of that name. The London Sinfonietta is notable for the depth and variety of its recording catalog, which numbers well over 80 items in the digital era, plus LPs before that. Some of the group's albums have appeared on major labels such as Deutsche Grammophon, CBS/Sony Classical, Decca, and EMI, while others have been issued by smaller contemporary music specialist labels, including the group's own London Sinfonietta label. The London Sinfonietta was heard on the album Luke Bedford: In the Voices of the Living, issued on the NMC label in 2023. ~ James Manheim