Metallica bassist Robert Trujillo explained why he and guitarist Kirk Hammett were happy to take risks with their “Kirk/Rob Doodle” jams during the band’s concerts. Each show sees the pair attempting a cover version that they’ve selected because of its local connections to the place they’re playing, with choices having included ABBA in Sweden, Bachman-Turner Overdrive in Canada, Prince in Minnesota and Garbage in Wisconsin.

“Sometimes it gets a little bit challenging to decide on an artist or a song,” Trujillo told Rolling Stone in a recent interview. “But when you find the right song, it’s really cool. It’s a way for Kirk and I to show honor and respect to some of the songwriters in the bands from that particular area.”

You can watch some of their "doodles" below - and we've collected nearly every one right here.

He reported that the best results came when he’d learned lyrics in a foreign language. “I’ll sing some obscure country song from the Czech Republic and I find out that this song is something every young person grew up with from the late '70s on,” he said. “In Barcelona, we did a flamenco song by a Catalan artist and people were freaking out. It’s the same thing in Helsinki. The song we covered was apparently the equivalent to the Ramones in that country, so you’re striking at an emotional connection and it ends up being on the national news.”

Trujillo said their approach was more relaxed when touring the U.S. – as they are now – and they could “bust out a classic R&B song, a country song, a punk rock song – and to me, that’s the beauty of it.” He added, “You can’t phone it in. You always have to create the arrangement, do the homework; and I give it my best shot and I get Kirk to mostly give it his best shot, too. That’s how we roll.”