Thanks for sharing. I should try to transcribe some of his bass work from those videos.Really?
There're many solo concerts by Frank Marocco, Richard Galliano and many others.
Of course I knew Marocco and also his sheet music. The sheet music (Jazz Accordion 1 +2), however, with a few exceptions, has only a very simple bass notation. Very much just Oom-Pa or Tango / Swing like style (chord + bass at the same time) plus a few simple runs.