There’s one suspect who’s name contains as many letters as the number of the symphony, indicating the time of day when Jo allows himself a glass of wine.
His name sounds a bit like Jo’s favourite sort of grapes.
He’s innocent.
Now you've nearly made it! Hurry up the Mainstreet until you reach Fanny-Elßler-Gasse. Hopfully you'll catch the thief there! I'm sure Jo will reward you with a drink afterwards.