I have a pair of backrollers and, when I'm going to play a concert, I stuff my usual clothes-stuff into my panniers, strap my saxophone to my back (backpack style case), and use the shoulder straps of the panniers to strap my collapsible music stand to the top of my rack such that it is partially supported by both panniers and the rack.

Is that close enough? It seems to work reasonably well for me.

(I picked up a used Yak for $100 this week so I won't be doing the stand on the panniers bit again, though.)