All over France--all over the world, in fact--musicians of every type will be performing, in every venue imaginable: from public parks to cafe terraces, from elegant châteaux to village squares. Anyone who wants to can come out and play: soloists, full orchestras and everything in between. I read that almost 8% of the country, some five million people, have played an instrument or sung in public at Fête de la Musique! The rules state only that all musicians must donate their time and that all concerts should be free. The event was launched in France in 1981 and this year, 700 cities in 120 countries will participate. (For the program in countries other than France, try here. In the US it's called Make Music and you'll find all the info here.)
To find out who's playing where in France, don't bother checking the festival site. Instead try a local listings site like Time Out (for Paris and Nice)...or Le Parisien Etudiant for Provence and other regions. If you Google search "Fête de la Musique" and your village, you'll get lots of good results. Or, ask at the Tourist Office, check out the signs around town or just grab your friends and go...