The folk-rock band opened in a hush, with singer Matt Gervais crooning the Eddie Vedder section and picking the song's electric guitar riff. Co-frontman Jonathan Russell took on the Cornell role, harmonizing and belting the chorus. Their bandmates kept the track at a subdued simmer with violin and muted toms.
Before the performance, Gervais shared a charming story about meeting Cornell and Soundgarden bandmate Matt Cameron as music-loving kids in Seattle.
"When I was a kid growing up there, everybody was trying to play music or skateboard," he said. "We were trying to do both. It was a day we were jamming out in the basement at my parents' house, playing music. We were taking a break and trying to do the skateboarding part. So we were out on the sidewalk, and we looked out in the neighbor's yard, and we saw a couple guys checking out a motorcycle. We looked a little closer and realized it was Matt Cameron and Chris Cornell from Soundgarden sitting right there."
Surprised by the celebrity sighting, the budding musicians walked back to the basement, left the garage door open, "turned the amps up as loud as [they could]" and started playing Soundgarden's "Fell on Black Days."
"About a minute later, we see Chris Cornell come lumbering into the room," he continued. "And with a sly little smile, he says, 'You guys are playing it a little fast.' It was an amazing moment for a kid, if you can imagine. We got to chat with them for a little while and get a sense of who they were as people, which is an amazing thing. And he was nothing but the sweetest person in the world. I always thought we'd get the chance to meet him again, but as we know now, we're not gonna get that chance."
The Head and the Heart's full Austin City Limits set will air this fall on the upcoming season.