Alex Honnold doesn’t play any free solo by ear. 

And part of his preparation means having the proper music to back his epic climbs—including his Jan. 24 (Jan. 25 local time) climb up Taipei 101, the 11th tallest building in the world standing at 1,667 feet in the capital of Taiwan.

“It was mostly Tool,” Alex revealed to Variety of his playlist in an interview published Jan. 24. “It’s a random playlist that I made, that I shared with production. I made it months ago while I was driving. I’ve been training to it a bunch. Basically, rock music that I’ve liked my whole life.”

But beyond liking the genre, the progressive metal band’s music played a practical role, too—especially when it came to navigating the skyscraper’s architecture, including the geometric façade dubbed bamboo boxes and the spiraling metal “dragons” decorating the corners.

“Part of the appeal of music is that actually it helps me with pacing,” Alex explained. “Each bamboo box had been taking me about five to six and a half minutes. I just know how long the songs are. So it gives you a sense of if you’re going fast or slow.”