I was saved by this man...
He was tuning the piano, interspersing repeated individual notes with the occasional burst of a tune. I went around the other side of the building, an art gallery, to go in and find out more. I got inside, but was stopped by someone else before I could reach the piano-tuner. He told me the gallery was actually closed. The piano was being tuned in readiness for this evening's private view, before opening to the public tomorrow (The Bicha Gallery spring show - guest artist Michael Kenny). I should have found out whether the tuner was also the pianist.