The Downtown Denver Partnership sprung a sweet surprise on 16th Street Mall strollers last summer when it threw the mall's first Make Music Denver street festival, a participatory free-for-all that celebrated beats and blasts and reverberations from masses of musicians of all skill levels and age groups. Inspired by an international event with roots in France's Fête de la Musique, which started more than ten years ago, Make Music Denver invited professional ensembles, independent bands and armies of instrumentalists to gather on the mall and perform for free. There were mass-appeal, same-instrument combos throughout the day, featuring groups of ukuleles or fiddles or guitars. There were drum circles. There were teen rock bands. There were jazz combos and symphonic sections, and plenty of opportunities to join in or just sit back and enjoy. The basic idea behind Make Music Denver — that everyone, from concert pianists to three-year-old toddlers beating on a pan, makes music — is a winner; the fest will return on June 21.