It was released on 30 November 2011 by Scene Nation Oy and Sony Music in Finland, then on 2 December in Nuclear Blast in the rest of Europe and Roadrunner Records worldwide.

The orchestration demos he had received from Pip Williams were described as "beautiful, twisted, tribal and cinematic stuff".

[15] On February 23, three interviews were released on the website - one each with composer Tuomas Holopainen, director Stobe Harju, and producer Markus Selin.

[17] This also led to changing the title of the track with the same name, but the song "Storytime" still includes the word "imaginarium" in the lyrics.

[19] A week later, the band released the Imaginaerum cover, track list and commentary on each song written by Holopainen.

The planning phase of the album started in the beginning of 2008, while Holopainen was on the Dark Passion Play World Tour (October 2007 - September 2009).

[7] In March 2010, Holopainen finished writing the music for the last song,[9] while some lyrics still were unfinished,[10] and on June 2, the pre-production demo had been recorded.

[7] In the summer of 2010, the band (except for singer Anette Olzon, who was pregnant at the time) gathered for rehearsal in the Finnish village of Sävi.

[32] Around New Year, Vuorinen had finished all comp tracks and about half of the leads to the album, planning to record acoustic and solo sections after the orchestral and choir sessions in February.

Most players of the 53-piece orchestra had already worked with the band on the previous albums Once (2004) and Dark Passion Play (2007), including the orchestral arranger Pip Williams.

This included some additional percussion and tribal drums, as well as the guest recordings of Troy Donockley and Pekka Kuusisto.

[14] According to Holopainen, the film has evolved radically from the original plan, while still retaining the main spirit of the foundation.

[41] According to drummer Jukka Nevalainen, "this is not a concept album per se", but it's "a coherent package from the beginning to the end".

[30] The album has been described as following a natural development from Dark Passion Play, inspired greatly by film scores.

Like Dark Passion Play as well as Once and Century Child it features a live orchestra, again orchestrated by Pip Williams.

The orchestrations have been described as "beautiful, twisted, tribal and cinematic", but will not be featured on every track as it was on Dark Passion Play.

Imaginaerum is the first Nightwish album since their debut that features no music written by the guitarist Emppu Vuorinen.

The reason for this, according to Vuorinen, is that after the long and exhausting touring for Dark Passion Play, he had no interest in touching his instrument for months.

Holopainen has cited three major influences on the album — film director Tim Burton, author Neil Gaiman and painter Salvador Dalí.

[12] Musical influences include Hans Zimmer, Danny Elfman, Ennio Morricone, Christy Moore, Van Halen and Pantera, and one song especially - "Rest Calm" - is inspired by death/doom giants Paradise Lost and My Dying Bride.

The song also introduces the "snow flake theme" of the album and movie, as the Finnish word "taikatalvi" means "magic winter".

[44] He has also said that it greatly represents the band as a whole, with "punchy riffs and a melodic chorus" and an orchestra heavy C-part.

[42] "Ghost River" has been described as "a duel between the Devil and Mother Gaia", and is more theatrical and "weirder" than the rest of the album.

[42] "I Want My Tears Back" features Troy Donockley on pipes, and is according to Holopainen one of the more approachable songs on first listen, as well as a possible future single.

[42] "The Crow, the Owl and the Dove" is one of only two ballads in the album, co-written by Holopainen and bassist-vocalist Marko Hietala, who has written several songs for the band in the past.

Holopainen has pointed out that it's "kind of funny that the most poppy ballad on the album is composed by the most metalhead dude in the band".

"[55] Steve Harris, the leader, bassist founder and main composer of Iron Maiden, chronicles his great appreciation for the sound of the band in a statement: “When I heard [2007’s] Dark Passion Play, I couldn't believe it.

Except what is seen on the album, this version also features more parts of the roller coaster as well as several zeppelins floating in the air above the park.

[20] The cover to the first single, "Storytime", was also done by Toxic Angel, and ties together with the themes of snow, the blue colours and the roller coaster.

The Young Musicians London also contributed vocals, led by Lynda Richardson and co-ordinated by Jenny O'Grady.