If you haven’t heard of Gnarls Barkley, you will soon. Earlier this month, the collaboration of DJ Dangermouse and Cee-Lo stepped into a brave new world with the psychedelic soul single “Crazy.” The song made history as the first to reach No. 1 in sales based on downloads alone. The duo’s album, St. Elsewhere, won’t be available in the United States until May 9, but you can listen to the single at www.gnarlsbarkly.com, or — even better — download it for free as part of DJ Audio1’s Rhymes and Beats Hiphop-cast No. 5. Along with playing a handful of weekly digital-radio shows, San Francisco’s Audio1 regularly posts his gnarls-ly blends of old-school and up-and-coming artists for folks on the go.