Question: Beatles Forever was an unreleased song by which English rock band?
Context: "The Palace of the King of the Birds" is a song by the English rock band the Beatles.  It was written by Paul McCartney and recorded by the band during the "Let It Be" album sessions from 6–9 January 1969 at Twickenham Film Studios.  The song is five minutes, four seconds long (the 6 January session is fourteen minutes one second long and turned into a loose jam), and was recorded with the demo of "Carry That Weight".  The song was later forgotten, until McCartney recorded a still unreleased version, in his solo recordings, named "Castle of the King of the Birds", for the unreleased album "Rupert the Bear", sometime in 1978, with Wings and went for a minute, forty two seconds. The Electric Light Orchestra (ELO) are an English rock band formed in Birmingham in 1970, by songwriters/multi-instrumentalists Jeff Lynne and Roy Wood with drummer Bev Bevan.  Their music is characterised by a fusion of Beatlesque pop, classical arrangements, and futuristic iconography.  After Wood's departure in 1972, Lynne became the band's leader, arranging and producing every album while writing virtually all of their original material. Shin'ya Waku (深夜枠 , "Late Night Broadcast Slot") , also known by its English title The Midnight Broadcasting is a compilation album by Japanese rock band Tokyo Jihen, released on August 29, 2012.  It predominantly compiled B-sides from the band's singles, as well as a DVD exclusive song and a previously unreleased song, "Tadanaranu Kankei". Exit Lights is a remix album by Christian rock band Falling Up, released on September 12, 2006.  The album is composed of remixes of the band's best known songs from "Crashings" and "Dawn Escapes", and a previously unreleased song, "Islander."  Genres incorporated here include dance-pop ("Escalates"), rapcore ("Moonlit"), goth rock ("Exhibition"), and post-hardcore (Cascades), along with heavy electronic influence on all the songs.  The album marks a complete departure from the band's original nu metal style to an experimental rock sound; as a result, the only song that features a heavy rock style is "Cascades (From In the Forest Cascadia)". Living in a Dream is the first live album and DVD by the Texas blues rock band Arc Angels, their second album over all.  The first disk of the album contains the majority of a show recorded March 26, 2005 at Stubb's Bar-B-Q in Austin, Texas.  The show proved to be historic for the band, playing the entirety of their debut album, a then unreleased song, "Crave and Wonder" and a cover of Muddy Waters' "She's Alright."  This show also proved to be the Arc Angels' final with original bass guitarist Tommy Shannon.  The second disk contains 3 studio tracks recorded for specifically for this album in 2009 and the remainder of the 2005 show, the song "Spanish Moon."  The DVD contains the Stubb's show and interview footage, directed by Kyle Ellison and produced by Mark Proct and Charlie Boswell. The Beatles: Rock Band is a 2009 music video game developed by Harmonix, published by MTV Games, and distributed by Electronic Arts.  It is the third major console release in the "Rock Band" music video game series, in which players can simulate the playing of rock music by using controllers shaped like musical instruments.  "The Beatles: Rock Band" is the first band-centric game in the series, and it is centered on the popular English rock group the Beatles.  The game features virtual portrayals of the four band members performing the songs throughout the band's history, including depictions of some of their famous live performances, as well as a number of "dreamscape" sequences for songs from the Abbey Road Studios recording sessions during the group's studio years.  The game's soundtrack consists of 45 Beatles songs; additional songs and albums by the Beatles were made available for the game as downloadable content. "Beatles Forever" is an unreleased song by Electric Light Orchestra in 1983, intended for the album "Secret Messages", written by Jeff Lynne.  Originally, the album was planned to be a double album, but after shortened to a single album, "Beatles Forever" was abandoned.  It is the only "lost" track from the original album not to appear later as an official bonus track or part of a compilation.  However, the chorus part of "Beatles Forever" was used by Lynne on his "Video! " solo single. Esenciales: Sol is a CD compilation album (seventeenth overall) by the Latin American Mexican rock band Maná.  It is one of three greatest hits compilation albums, along with "" and "", with remastered versions of all their best-known songs.  "Esenciales: Sol" includes a previously unreleased song, "Te Llevaré Al Cielo", and a bonus track, "Tonto En La Lluvia'" (in English:"Fool in the Rain"), a song by Led Zeppelin from their "In Through the Out Door" album.  The album also includes two music videos. Kenny Loggins Alive is a live album by soft rock singer, Kenny Loggins.  Released in 1980, it contains material from Loggins' three previous solo albums, as well as a previously unreleased song "All Alone Tonight", "I'm Alright" (the theme from "Caddyshack") and a cover of The Beatles "Here There and Everywhere" (Loggins was known to have been a Beatles fan).  A movie recording of the same title is available with different songs. The Beatles Bootleg Recordings 1963 is a compilation album of 59 previously unreleased recordings by English rock band the Beatles, released on 17 December 2013, exclusively through the iTunes Store.  While it was initially only available for a few hours, it is currently available again for purchase.  The release was timed to extend the copyright of the 1963 recordings under EU law by 20 years – the EU protects recordings for 70 years only if they are formally released.  Officially unreleased recordings from the band's earlier recording sessions previously entered public domain in 2012.
Answer: Electric Light Orchestra