He played bass more often than people realise, and even owned a bass or two himself!

There are quite a few instances on record (as in "documented fact") of him standing in for bass players, or picking up the bass in a jam.
Here are a couple of photographs of a gig which he played with Johnny Winter - and to make it even more unusual, Johnny seems to be playing a Stratocaster, rather than his trademark Firebirds!
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Here he is with Noel Redding's beautiful old sunburst Jazz -
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And in the studio, with a P bass -
