Written and produced by ELO frontman Jeff Lynne, the double album is among the most commercially successful records in the group's history, selling about 10 million copies worldwide by 2007.

[6] Jeff Lynne wrote the entire album in three and a half weeks after a sudden burst of creativity while hidden away in his rented chalet in the Swiss Alps.

[10] Cash Box said that it begins "with simple chording which opens to a strumming beat" and that the "strings add panorama" and that "the vocals are characteristically crystalline and soaring.

"[11] "Sweet Talkin' Woman" serves as the band's "first real step into the disco sound [...] a string-laden pop tune whose dance-friendly edge helped it become a disco-era hit".

AllMusic's Donald A. Guarisco attributed its disco sound to "Bev Bevan's steady drum work" and "pounding piano lines, delirous bursts of swirling strings, and endlessly overdubbed backing vocals [that] mesh seamlessly to form an ornate but driving funhouse of pop hooks".

"[13] "Across the Border" begins with the same "clanging train" sound effect used on the ABBA song "Nina, Pretty Ballerina" and a violin solo by Mik Kaminski.

"[15] The song begins with an unusual segment where keyboardist Richard Tandy's keyboards emulate "the noise and cacophony of busy traffic", combined with "frenzied" string sections invoking "the oppressive atmosphere of being trapped in a city that never sleeps".

[17] "Jungle" takes a stylistic left turn, featuring "Tarzan effects, trumpeting elephants, a talking lion, and a Terpsichorean interlude" that Delve describes as part of the song's "unashamed goofiness".

In the final two minutes, the previously stripped-back arrangement is augmented with increasingly large layers of guitars and vocal harmonies, building to a "grand finish".

Side three of the release is subtitled Concerto for a Rainy Day, a four-track musical suite with common themes of the weather, inspired by the "relentless rain" Lynne experienced in Switzerland while writing the album.

[27] Jeff Lynne has told the story of how he wrote the song:[28] The weather had been really bad, and then one day I got up and it was fantastic, the sun was brilliant and shining, all the mountains were lit up and this mist had gone away.

[28] Mark Beaumont said that the first track on Side 4, "Sweet Is the Night", "[sweeps] from an elegant glam-funk strut to a chorus that [is] essentially All The Young Dudes base-jumping.

[33] "The Whale" is an instrumental track that begins with a "flurry of aquatic, atmospheric effects", and uses the stereo soundscape greatly to "convey the ocean's space and expanse.

"[34] Lynne wrote the song after watching a TV episode about the hunting of whales, and a part of the proceeds from Out of the Blue were donated to environmental advocacy group Greenpeace.

[34] ELO historian Barry Delve praised the song, calling it a "a great one to listen to in headphones",[34] though Mark Beaumont was more critical, naming its "lumbering, ambient depths" as one of the worst moments of Out of the Blue, alongside a "shonky side two".

"[52] Billy Altman of Rolling Stone said that the album was "meticulously produced and performed" and showed the influence of the Beatles, the Beach Boys and the Bee Gees.

However, he detected a lack of passion in the work, which he dismissed as a "totally uninteresting and horrifyingly sterile package" and "All method and no madness: perfectly hollow and bland rock Muzak.

"[48] With an 8.1/10 score in a 2007 review Rob Mitchum of Pitchfork wrote "Calling in the string section and commissioning the spaceship cover-art may be a big gamble, but Out of the Blue is proof of how good it can sound when the grand approach works.

"[50] Dan MacIntosh of PopMatters gave a 7/10 score saying "Even with all the excessive rock trappings inherent during ELO’s era, Out of the Blue nevertheless stands up well as a creative endeavor.