"Computer Blue" is the fourth track on Prince and the Revolution's soundtrack album, Purple Rain. In the film, the song represents Prince's angst at the budding relationship between the characters played by Morris Day and Apollonia. The song was composed by Prince, with credit to his father, John L. Nelson for the guitar solo based on an untitled piano piece by Nelson. Prince titled the piece "Father's Song" and recorded it on piano for the film, though on screen it was portrayed as being played by Prince's on-screen father, actor Clarence Williams III.

"Computer Blue" was originally recorded at Sunset Sound in Los Angeles in early September 1983. Prince along with Wendy & Lisa and sound engineer Susan Rogers set about recording what would later end up being placed on the album Purple Rain, albeit in a very heavily edited form.

The song begins with spoken lyrics by Wendy & Lisa which suggest a dominatrix-type relationship. The song then becomes a very guitar-oriented number with rock music screams. The released version only has one verse. The version of the song that debuted at the First Avenue nightclub in Minneapolis, Minnesota had a second verse, as did the song as it was originally recorded.

Originally conceived as a 14-minute opus, "Computer Blue" would later be edited down several times for inclusion on Purple Rain; the song was edited from a fully mastered 7:30 down to its current length when "Take Me with U" was added to the album at the last minute.

The full-length version of the song contains extended instrumental solos and additional lyrics. Also present is a repeated synthesizer segment with a sing-a-long phrase "nah nah nah nah nah", which was often played in live versions of the song. The synth part, without the vocals, even made it into the film Purple Rain as the Revolution was rehearsing while waiting for Prince to arrive. The track ends with three full minutes of screeching feedback. A shorter version, 12 minutes in length, was the one edited down to the album's version, and the feedback from this version forms the segue to "Darling Nikki" on Purple Rain itself. Widely regarded by the hardcore fan base as a musical masterpiece, the original unedited recording features the infamous "Hallway Speech" (as termed by fans) about emotions likened to different rooms. During the Purple Rain performances at the end of the song before "Darling Nikki", the "Righteous 1" speech spoken by Wendy & Lisa cut from the final version of the track is played.

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