On Saturday, the avant-garde duo Bluebrain held their final Boombox Walk at the U.S. Botanic Garden. Among the welcoming greenery and flowers, Ryan and Hays Holladay organized the group of participants, handing everyone who had RSVP’d their respective cassettes, CDs and MP3 files. On their signal, everyone pressed play and walked around the garden en masse, creating a huge, mobile orchestra. This was the final walk in the series, after previous events on the National Mall at 2010’s Cherry Blossom Festival and at Dupont Circle in August 2009. DCist photographer Brandon Hirsch showed up to document the event.