I immediately could tell this is not a signature of Bix's (Leon Bix).
Good thinking, Sue and Jamaica, for the suggesion that this signature could be that of Charles Burnette Beiderbecke, (Bix's older brother and my Grandfather) since my Grandpa Burnie did manage the music department at Petersen, Harned and Von Maur and also went by 'Bix' for a number of years.
Therefore, I, like you, Albert, it would be a good idea to see if it resembled my Grandpa Burnie's signature.
I looked up some documents and found where Grandpa Burnie had written the name 'Bix' eight times.
There is NO resemblance of Charles Burnette Beiderbecke's (aka 'Bix') signature to the signature up for auction.
The capitol letter 'B' in the signature up for auction is consistently different from the 'B' in my Grandpa Burnie's signature. Buyer: Beware!!
On a different note, I agree with Albert. The photo is very intriguing, so much detail. It's fun to study, but a curiosity to ponder re: what is it a photo of and who signed 'Bix Beiderbecke' on it??!!!