The Theatre of Eternal Music

The Theatre of Eternal Music (later sometimes called The Dream Syndicate) was an avant-garde musical group formed by American composer La Monte Young in New York City in 1962. The group was initially formed in order to play and develop Young's compositional idea of The Tortoise, His Dreams and Journeys, which involved improvisation within strict predetermined guidelines set by Young.

The first group (1962–1964) of performers consisted of La Monte Young, Marian Zazeela, Angus MacLise, and Billy Name. From 1964 to 1966, it consisted of La Monte Young (voice, saxophone), Marian Zazeela (voice, lighting), John Cale (viola), and Tony Conrad (violin), with sometimes also Terry Riley (voice). Since 1966, Theatre of Eternal Music has seen many permutations and has included Garrett List, Jon Gibson, Jon Hassell, Rhys Chatham, Alex Dea, Terry Jennings, and many others, including some members of the various 1960s groups. The group's self-described "dream music" explored drones and pure harmonic intervals, employing sustained tones and electric amplification in lengthy, all-night performances.

Archival recordings of the group's influential mid-1960s performances remain in La Monte Young's archive. None have ever seen official release following a dispute over compositional credit between Young and the pair of Conrad and Cale. Nonetheless, a 1965 bootleg recording removed from the archive by Young's first archivist, Arnold Dreyblatt, was controversially released in 2000 by Table of the Elements in CD as Day of Niagara. Other bootlegs of Theatre of Eternal Music have appeared online via file-sharing sites.