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 a "forlornly pretty" ballad, according music critic Barney Hoskyns.
The song was thought to be never performed live by Black Sabbath until 1995, with Tony Martin on vocals. There is however a recording of song being performed live with Ozzy Osbourne in 1973 in New Zealand.
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 No. 1 in the UK Singles Chart. It also reached No. 1 on the Kerrang! UK Download Chart.
According to the Ozzy Osbourne official website, the single sold over one million copies.
This version of the song, was named #27 of the "50 Worst Songs of the '00s" in a 2009 Village Voice article.