Klapa singing is something that is highly popular around the Dalmatia region of Croatia. Klapa, a form of a cappella singing, can often be heard in public areas during peak hours of day; so it isn't to hard to find a performance. I would recommend asking your hotel concierge about performances in the area as they may know of scheduled performances.
I was able to sit in and listen to a performance from the local Motovun Klapa club at the Church of St. Stephen where the groups melodies echoed throughout the church and carried onto the quiet streets outside. Most of the songs were in Croatian but the group also sang a few popular English ballads as well.