The "Pure Energy" vocal comes from Leonard Nimoy's character Spock on the TV series Star Trek
. In the 1967 Season 1 episode "Errand of Mercy," Spock and Captain Kirk visit the planet Organia, where their citizens have advanced beyond the need for physical bodies. When two of them vanish in front of them, Spock says, "Fascinating. Pure energy. Pure thought. Totally incorporeal. Not life as we know it at all."
At the beginning of the song, there's another sample from the series: DeForest Kelley's character Dr. McCoy saying, "It's worked so far, but we're not out yet."
Two other songs on the album also use Star Trek
samples: "Over the Sea" and "Walking Away
." Just one problem: the samples weren't cleared and the record company refused to release the album until they were. The album was slated for release in December 1987, but got stuck in limbo when nobody from Paramount would respond to requests to authorize the Star Trek
clips. The breakthrough came when the band's A&R man contacted Nimoy's son Adam and asked for help. Adam Nimoy brought the issue to his father's attention, and the samples cleared. The album was released in June 1988 after a six-month delay. "What's On Your Mind" reached its chart peak on the Hot 100 in October.