"Unchained Melody" is a 1955 song with music by Alex North and lyrics by Hy Zaret. North used the music as a theme for the little-known prison film Unchained, hence the name. Todd Duncan sang the vocals for the film soundtrack. It has since become a standard and one of the most recorded songs of the 20th century, most notably by the Righteous Brothers. According to the song's publishing administrator, over 1,500 recordings of "Unchained Melody" have been made by more than 670 artists in multiple languages.

In 1955, three versions of the song (Les Baxter, Al Hibbler, Roy Hamilton) charted in the Billboard Top 10 in the United States, and four versions (Al Hibbler, Les Baxter, Jimmy Young and Liberace) appeared in the Top 20 in the United Kingdom simultaneously, an unbeaten record for any song. The song and "Do They Know It's Christmas" are the only songs to reach number one in four different recordings in the UK. Of the hundreds of recordings made, it was the July 1965 version by the Righteous Brothers, performed as a solo by Bobby Hatfield, that became a jukebox standard for the late 20th century. This version achieved a second round of great popularity when it was featured in the 1990 blockbuster film Ghost. In 2004, it finished at number 27 on AFI's 100 Years...100 Songs survey of top tunes in American cinema.

In 1954, North was contracted to compose the score for the prison film Unchained. North composed and recorded the score, and then was asked to write a song based upon the movie's theme. North asked lyricist Hy Zaret to write the lyric, but Zaret initially declined, saying he was too busy painting his house. North was able to convince him to take the job, and together they wrote "Unchained Melody." Zaret refused the producer’s request to include the word "unchained" in his lyrics. The song eventually became known as the "Unchained Melody" even though the song does not actually include the word "unchained". Instead, Zaret chose to focus on someone who pines for a lover he has not seen in a "long, lonely time". The 1955 film centered around a man who contemplates either escaping from prison to live life on the run or completing his sentence and returning to his wife and family. The song has an unusual harmonic device as the bridge ends on the tonic chord rather than the more usual dominant chord. With Todd Duncan singing the vocals, the song was nominated for an Oscar in 1955, but the Best Song award went to the hit song "Love Is a Many-Splendored Thing".

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