"Baroque" sounds close to the word "broke". An instrument that is "broke" or broken is an instrument that no longer functions as it should due to some kind of damage. Baroque refers to a style of European architecture or music. This joke can be taken literally, that there is a repair shop of music instruments of the baroque period, or can be understood as "there is a repair shop for broke musical instruments". 
There ' s a repair shop for baroque musical instruments .