Billy Sheehan is a virtuoso bass player who has played with a number of bands including Mr. Big, who opened for Rush on both the Presto and Roll the Bones tours. Rush Tour Forum user Tench Frickler dug up this neat audio clip on Billy Sheehan's website. It's a clip of Billy jamming with Alex Lifeson and Neil Peart before an April 5, 1990 show in San Diego where apparently Geddy was late for the sound check. The original clip is in realaudio format and can be heard here. But MitA was kind enough to convert the clip to mp3 format. You can access the mp3 clip directly here or use the player above.