Out of the Blue is the seventh studio album by the British rock group Electric Light Orchestra (ELO), released in October 1977. 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.

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. It took a further two months to record in Munich. Side three of the original double LP consisted of the symphonic Concerto for a Rainy Day, composed of four separate tracks which together made up a cohesive suite, instead of one continuous track. The inclement weather effects heard on "Concerto" were real and recorded by Lynne during a very rainy summer in Munich 1977. The Concerto suite would be Lynne's last dabbling in symphonic rock. It was one of the first pop albums to have an extensive use of the vocoder, and helped to popularize it.

Side three of the release is subtitled Concerto for a Rainy Day, a four track musical suite based on the weather and how it affects mood change, ending with the eventual sunshine and happiness of "Mr. Blue Sky". This was inspired by Lynne's experience while trying to write songs for the album against a torrential downpour of rain outside his Swiss Chalet. "Standin' in the Rain" opens the suite with a haunting keyboard over a recording of real rain, recorded by Jeff Lynne just outside his rented studio. Also heard at the 0:33 mark of the song, which marks the beginning of The Concerto, is thunder crackling in an unusual manner voicing the words "Concerto for a Rainy Day" by the band's keyboardist, Richard Tandy. At around the 1:07 mark, the staccato strings play a morse code spelling out "ELO". The band used the song to open their 1978 World Tour Out of the Blue concerts.

"Big Wheels" forms the second part of the suite and continues with the theme of the weather and reflection. Apart from its inclusion on the Out of the Blue album, the song has never appeared on any of the band's compilations or as a B-side until 2000, when Lynne included it on the group's retrospective Flashback album. "Summer and Lightning" is the third song in the suite. The raining weather theme is continued throughout the track though the mood and lyrics are more optimistic. "Mr. Blue Sky", an uplifting, lively song celebrating sunshine, is the finale of "Concerto for a Rainy Day" suite. It is the only piece from the Concerto to be excerpted as a single.

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