Songfacts®:

• The voice on the hook ("I'm going through changes...") is Ozzy Osbourne. It's a sample of a 1972 song called "Changes" by Ozzy's band Black Sabbath, one of the few ballads in their catalog.
  
  The sample frames verses where Eminem revisits a dark time from a few years earlier when his best friend Proof was killed and Em went into a deep depression as he got addicted to prescription drugs ("Now I'm poppin' Vics, Percs and Methadone pills...").
  
  The time frame here is 2005-2009. After putting out his album Encore in 2004, he started to sink. After Proof died in 2006, he spent most of his time at his mansion, sinking even deeper. He started to emerge from his funk in 2008 and released the album Relapse in 2009. That album largely deals with his struggles, as does his next one, Recovery, which includes "Changes." Recovery had a lot more bite and put Eminem back at the top of the rap game. Singles from the album include "Not Afraid" and "Love the Way You Lie."
• Emile Haynie produced this song and is credited as a writer along with Eminem and the members of Black Sabbath who wrote "Changes." This was early in Haynie's career. He went on to produce hits for Bruno Mars ("Locked Out of Heaven"), Lana Del Rey ("Love") and Camila Cabello ("Consequences").
• The Black Sabbath ballad "Changes" didn't get much attention when it was released in 1972, but it changed form decades later to pervade the culture, starting in 2003 when Ozzy Osbourne and his daughter Kelly recorded a modified version with some of the lyrics altered to make it about a father and daughter drifting apart. Released as a single, it became Ozzy's only UK #1 hit.
  
  Eminem brought it to a new audience with this song, and in 2017 a soulful cover by Charles Bradley was used as the theme song to Big Mouth on Netflix series.