The song's piano melody was composed by guitarist Tony Iommi, who was experimenting with the instrument in the studio. "Changes" is a ballad inspired mainly by Bill Ward's ongoing breakup with his first wife. The lyrics were composed by bassist Geezer Butler, and vocalist Ozzy Osbourne has referred to the song as "heartbreaking". The song was quite different from Black Sabbath's previous songs, given that this one was characterized by a melodic and downbeat soft rock vibe in sharp contrast to the hard guitar-driven sound the band had become famous for.
The song was never performed live by Black Sabbath until 1995, with Tony Martin on vocals.
Three decades later, Ozzy recorded yet another version of the song, this time with his daughter, Kelly Osbourne as a duet. The revised lyrics for this version, released in 2003, reflect the moments of their life together. The single reached #1 in the UK. It also reached #1 on the Kerrang! UK Download Chart. It also became Birmingham's Big One and was nominated for a Grammy.
According to the Ozzy Osbourne official website, the single sold over 1 million copies.