I believe in May there is a Classical music festival with free concerts in many venues. I caught one when I was there in 95'. Often there are bands busking on the Charles Bridge and in front of Hradcany Castle. I spent my first decade in Czechoslovakia (as it was then) and heard quite a lot of Brass band music - it comes from the Austrian and German military tradition - the older tradition was fiddle and bagpipe (which were bellows pipes and the piper often sang at the same time). The cimbalom, a dulcimer played often with 2 hammers in each hand is commonly played in the eastern parts of the republic (Moravia) where the music is markedly different, more greek and gypsy influenced. (the instruments are usually fiddle, cimbalom, clarinet and vocals) I dont know where you could hear that in Prague but one well known venue is a pub called U Fleku (At Flek's) which has live music and several cabaret rooms. its Touristy. enjoy your holiday. Petr