Medieval Manuscript Appears to Show a Man Playing Air Guitar

Medieval book historian Erik Kwakkel jokes:

Medieval fact you didn't know: carefully monitored competitions of playing air-guitar were held annually

These competitions were instituted by Bill & Ted during their excellent adventure through time.
Assuming that I understand the annotation correctly, this image can be found in the Engelberg 3 manuscript, which is a Twelfth Century copy of part of the bible.