(See how much you like opera?)
From here I read:
On November 20, in the Central Market in Valencia, Spain, a piano was heard playing over the sound system, and a young fruit-seller suddenly started singing Alfredo’s Act I music from Verdi’s La Traviata from inside his stand. He was joined by a soprano female vendor, singing Violetta.
Then another tenor broke in, then another soprano, as a bemused crowd looked and listened in appreciation. At the end, there were three couples, indulging in a little competitive singing, handing out sparkling wine in champagne flutes, waltzing with passersby – and passing out leaflets pushing the opera.
(I’m not hearing a piano, though. Accordion maybe?)