Working as singer / musician in Poland

Hi,
I'm planning to study in Poland, probably in Wroclaw, next year, and combine study with working. I've read that you need a work permit for most of the types of work, but i'd like to know if it's needed a work permit to work as musician for example in restaurants, hotels, etc. I ocassionaly work as a musician in my home country (Guatemala City) and it would help a lot if someone could help clarify this.

Thanks in advance :)