"Sign o' the Times" is the lead single from American musician Prince's 1987 album of the same name. The song was originally intended for two separate Prince albums meant to be released in 1986, that were both shelved: Dream Factory and Crystal Ball. (Many of the tracks from both of these albums ended up on the album Sign o' the Times.) Prince sings and performs the entire track except for some backing vocals by then-girlfriend Susannah Melvoin, sister of Wendy, then a guitarist in The Revolution. "Sign o' the Times" was written and composed on a Sunday, when Prince usually wrote his most introspective songs.

The song proved popular upon release, topping the R&B chart, and reaching number three on the Billboard Hot 100 and number 10 on the UK Singles Chart. In 2010 Rolling Stone ranked "Sign o' the Times" at number 304 on their list of the 500 Greatest Songs of All Time. In 1987, both NME and Village Voice's Pazz & Jop critics' poll named "Sign o' the Times" the best single of the year. The song is also included in The Rock and Roll Hall of Fame's 500 Songs that Shaped Rock and Roll.

The song was constructed by Prince almost entirely on the Fairlight sampling synthesizer, which provides the primary keyboard riff and sampled electronic bass sounds heard on the track. Unlike some artists, Prince did not program new sounds for this song. He simply used the stock sounds the Fairlight offered, including the famed "orchestra hit" towards the end of the composition. The single marked a shift from those pulled from the albums Parade and Around the World in a Day, with a spare, electronic-based arrangement, simple drum machine hits and minimal stacked synth patterns, as well as a bluesy, funk-rock guitar part (cut from the single edit of the song). The record was noticeably bluesier and more downcast (both melodically and lyrically) than any of Prince's previous singles, addressing various socio-political problems including AIDS, gang violence, natural disasters, poverty, drug abuse, the Space Shuttle Challenger disaster and impending nuclear holocaust. This record showcased Prince's ability to merge classic and modern rhythm and blues characteristics into one song.

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