Ritchie Blackmore, Deep Purple's central force since their creation, left the group after Stormbringer to form his own group; this is Deep Purple's first record with new guitarist Tommy Bolin.

The album takes off in the chunky funk-rock style of Purple's last two albums. Distinctions don't develop until the material becomes familiar. Like Blackmore, Bolin establishes tension between Purple's solid rhythm foundation and his own sustained clarity and agitated upper-fret playing. While Blackmore was largely confined by this style, Bolin employs it as only one of many. His more flexible approach to writing and arranging produces a more melodic and dynamic feel. With him, Purple's music has outgrown the predictability of the past. Textures replace a reliance on volume, and changes in tone and pace more frequently contrast and augment each other. There is evidence of give and take that Deep Purple hasn't shown for some time. David Coverdale's emerging songwriting talents combine with Bolin's in "Dealer." Lord's more sophisticated keyboard work surfaces in several tunes.

A visible attempt to experiment has expanded the group's music beyond the heavy-metal trap, and this could lead them to rediscover the progressive style that somehow vanished after In Rock.

“Help Me”

Joni Mitchell wrote and recorded this song for her album Court and Spark, but she had to switch from her regular band to make the song sound exactly the way she wanted. "I had attempted to play my music with rock & roll players," she told Rolling Stone. "They’d laugh, 'Awww, isn't that cute? She's trying to teach us how to play.'" Mitchell switched to a jazz band, Tom Scott’s L.A. Express, and scored the biggest hit of her career in the process.