"Trio" is an improvisation by the British

United Kingdom

The United Kingdom of Great Britain and Northern IrelandIn the United Kingdom and Dependencies, other languages have been officially recognised as legitimate autochthonous languages under the European Charter for Regional or Minority Languages...

 progressive rock

Progressive rock

Progressive rock is a subgenre of rock music that developed in the late 1960s and early 1970s as part of a "mostly British attempt to elevate rock music to new levels of artistic credibility." John Covach, in Contemporary Music Review, says that many thought it would not just "succeed the pop of...

 band King Crimson

King Crimson

King Crimson are a rock band founded in London, England in 1969. Often categorised as a foundational progressive rock group, the band have incorporated diverse influences and instrumentation during their history...

. It was released on their sixth studio album, Starless and Bible Black

Starless and Bible Black

Starless and Bible Black is an album released by the British progressive rock band King Crimson in 1974. Most of the vocal pieces on the album are satires and commentaries on the sleaziness and materialism of society...

.

The piece was recorded live at the Amsterdam

Amsterdam

Amsterdam is the largest city and the capital of the Netherlands. The current position of Amsterdam as capital city of the Kingdom of the Netherlands is governed by the constitution of August 24, 1815 and its successors. Amsterdam has a population of 783,364 within city limits, an urban population...

 Concertgebouw

Concertgebouw

The Concertgebouw is a concert hall in Amsterdam, Netherlands. The Dutch term "concertgebouw" literally translates into English as "concert building"...

, on November 23 1973. It is the most serene track on the album.

Although it is an improvisation involving only violin, bass guitar and Mellotron

Mellotron

The Mellotron is an electro-mechanical, polyphonic tape replay keyboard originally developed and built in Birmingham, England in the early 1960s. It superseded the Chamberlin Music Master, which was the world's first sample-playback keyboard intended for music...

, drummer Bill Bruford

Bill Bruford

William Scott "Bill" Bruford is an English drummer, percussionist, composer, producer, and record label owner. He was the original drummer for the progressive rock group Yes, from 1968-1972. Bruford has performed for numerous popular acts since the early 1970s, including a stint as touring...

is also given a writing credit, as the other members of the band viewed Bruford's decision not to play as a crucial choice.