In the Wake of Poseidon is the second studio album by the progressive rock group King Crimson. By the time this album was released, the band had already undergone their first change in line-up, however they still maintained much of the style of their first album, In the Court of the Crimson King. Also like their first album, the mood of this album often changes from serene to chaotic.
Greg Lake was the next member to leave, after Ian McDonald and Michael Giles left the band following their first American tour in 1969, after being approached by Keith Emerson to join what would become Emerson, Lake & Palmer in early 1970. This left Fripp as the only remaining musician in the band, taking on part of the keyboard-playing role in addition to guitar. To compensate, Sinfield increased his own creative role and began developing his interest in synthesisers for use on subsequent records.
Lake agreed to sing on the recordings for In the Wake of Poseidon (negotiating to receive King Crimson's PA equipment as payment). Eventually, he ended up singing on the band's early 1970 single "Cat Food" b/w "Groon" and on all but one of the album’s vocal tracks. The exception was "Cadence and Cascade", which was sung by Fripp's old schoolfriend and teenage bandmate Gordon Haskell. There does exist however, an early mix of the song with Lake singing a guide vocal which was unearthed and featured on the DGM site as a download. At one point, the band considered hiring the then-unknown Elton John to be the album's singer, but decided against it. Other former members and associates returned – as session players only – for the Poseidon recordings, with all bass parts being handled by Peter Giles and Michael Giles performing the drumming. Mel Collins (formerly of the band Cirkus) contributed saxophones and flute. Another key performer was jazz pianist Keith Tippett, who became an integral part of King Crimson's sound for the next few records (although Fripp offered him full band membership, Tippett preferred to remain as a studio collaborator and only performed live with the band once).
On 25 March 1970, the line up of Fripp, Lake, Tippett, Mike and Peter Giles taped a mimed performance of the single version of "Cat Food" for the following night's broadcast of BBCTV's Top Of The Pops. It was to be King Crimson's sole British TV appearance until 1981. This footage has long since been wiped, though several photographs taken backstage and of the dress rehearsal do exist.
With the album on sale, Fripp and Sinfield remained in the awkward position of having King Crimson material and releases available, but not having a band to play it. Fripp persuaded Gordon Haskell to join permanently as singer and bass player, and recruited drummer Andy McCulloch, another Dorset musician moving in the West London progressive rock circle, who had previously been a member of Shy Limbs (alongside Greg Lake, who recommended him to Fripp) and Manfred Mann's Earth Band. Mel Collins was also retained as a full band member.
The album opens with an a cappella piece called "Peace – A Beginning", which is reprised instrumentally in the middle of the album and vocally again at the end. The strongly jazz fusion-influenced "Pictures of a City" was originally performed live, often extended to over ten minutes and was called "A Man. A City". An example of such a performance can be found on the live album Epitaph.
The longest track on the album is a chaotic instrumental piece called "The Devil’s Triangle", which was built around quotations from Gustav Holst's "Mars: Bringer of War" from his The Planets Suite. King Crimson would have called the piece "Mars", as they had performed it on tour in the 1969 line-up, but were forbidden by the composer's legal estate. In 1971, a brief excerpt from "The Devil’s Triangle" was featured on the BBC television series Doctor Who. Also, the track samples the chorus from "The Court of the Crimson King", the title track from the band's first album, a studio technique known as xenochrony.