"Power Up" is a tribute to founding AC/DC rhythm guitarist Malcolm Young, who died in 2017 from effects of dementia at age 64. Malcolm is credited as a writer on all 12 tracks on "Power Up", along with his brother, AC/DC lead guitarist Angus Young.
"The riff for 'Through The Mists Of Time' came out, and Angus wrote the lyrics for that song, and I believe he captured everything - about the early days when the band started, when rock and roll was just carefree, when nobody gave a flying thought about anything except just having a good time and playing," Brian said. "And all this lovely innocence was gone. And I think [the lyrics] encapsulated [the sentiment]. To tell you the truth, every time I hear it, I still get a goosebump, and it's a tribute to Malcolm: 'Through The Mists Of Time'. And it's different. I don't know if it's different from anything we've done before, but it certainly stands apart."