Oh! Another one.
Trying to give you the story just as how it developed for me:
Got asked to dep on piano for rehearsals of some sort. Some players I knew and some new to me, and first we gathered around a cuppa. Great atmosphere. Someone had brought his granddad or summat, Jean (French male name), a friendly and humourous bloke if a bit silent - maybe uncomfortable in the situation.
As we proceeded to the rehearsal room, granddad followed us, which I thought was remarkable, but hey ... not my band!
So we start rehearsing, me highly concentrated on the notes, as this was sightreading.
Granddad sat to my side and a bit behind me. Looking half over my shoulder I noticed he was rummaging his bag and producing something from it, which irked me a bit, but I couldn't turn around and signal him to please stop. Notes, ya know.
Next thing is that I hear these immediately recognisable, bee-you-tee-full harmonica tones sent directly from the gods ... Granddad was only Jean-Baptiste Frédéric Isidore, flamin' baron of Thielemans. (Laughter ensued; they'd agreed to not let me in on this and to then watch my response.)