I just came across this clip from a couple years ago at a jam session with Andy Reiss (The Time Jumpers) and Ranger Doug (The Time Jumpers and Riders In The Sky) with Jeff Adams on trombone.
https://www.instagram.com/p/BVpOEkRF...on_share_sheet
I was playing my 1968 Guild archtop - trying to keep up with Ranger Doug's Stromberg. I was reading the chord changes off the iPhone on the trombone player's leg.