Mr. Big bassist Billy Sheehan has recalled the moment in 1990 when he stood in for Geddy Lee during a Rush soundcheck.

The 15-minute jam has been available online for some time, but Sheehan recently shared the first 10 minutes on Twitter. “Years ago, Mr Big was on tour w Rush on their Presto tour, Geddy was late for soundcheck -- stuck in traffic from LA to San Diego," he wrote. "They asked me to get up and jam w Neil & Alex for sound check, and recorded it. I played through Geddy's rig … ”

The incident took place during Mr. Big’s first tour, and Sheehan has said in the past that he took the opportunity to discuss bass playing with Lee. “Geddy is a wonderful person and an amazing bass player,” he said on one interview archived on his website. “We enjoyed touring with them very much.”

In 2011 he told MusicRadar that they’d often talk about playing bass and singing at the same time. “It's pretty tricky. I work at it a lot,” he said. “I can strum the guitar and sing all day long. But to play bass and sing at the same time, especially with some of the things I do with my right hand, it's hard. It doesn't come naturally, but it can be done. You just have to sit down and work out your parts. I'd sit and talk to Geddy Lee about [playing bass]. He's one of the sweetest guys around, by the way. But he told me that he has to work at it big-time. I don't know anybody who does it better than him.”

Sheehan’s latest band Sons of Apollo – which also includes former Journey singer Jeff Scott Soto, Guns N’ Roses' ex guitarist Ron "Bumblefoot" Thal and onetime Dream Theater members Mike Portnoy and Derek Sherinian – continue a U.S. tour that ends on May 20 in Washington, D.C., before a run of European, U.K. and Japanese dates.