One effect of learning to play upright is my constant observation of other upright players' technique. In this video, the bass player who plays with Pat Metheny has very unusual left hand thumb positions And and even Pat Metheny himself seems to have very unusual left hand thumb technique. For Pat. he may have been muting his low E and or A strings (not sure) but the upright player seems to have his LH thumb vertical in many spots. Given the strong emphasis on technique on upright (with good reason given how tough the instrument is to play and its size) I was curious what you think of the upright thumb use in this video. Interested in perceptions about Pat's thumb use if you care to comment, although he is a guitar player. One teacher I had years ago once said "when you're as good as [insert famous player here] you can do whateever you want.