Put some musical instruments in public spaces, and musicians (even homeless ones) will come play them. An idea worth stealing! From The Denver Post:
There's lots of love downtown. The Downtown Denver Partnership began placing pianos along the mall in late 2009, said spokesperson Sarah Neumann. All of the instruments were donated; the partnership received many of them just by asking on Craigslist. They started with eight pianos but grew the roster to the current 17. All of them are painted to match the seasons by local artists.