Bluebrain embarks on its final boombox walk on Saturday. (Tracy A Woodward/TWP)

The premise is pretty simple — bring “a portable cassette, CD or iPod enabled music device”to the Botanic Garden on Saturday, Bluebrain will provide you with music made specifically for this event, and everyone hits play at the same time and marches around as a walking boombox orchestra. (You’ll need to e-mail the band — bluebrainmusic at gmail dot com — today to let them know what format to bring your music on.)

The event is free and starts at 3 p.m. Be on time — it’s all about pressing play together at the beginning. And since the Botanic Garden is right next to the National Mall, consider it a perfect opportunity to dig back into Bluebrain’s album before or after Saturday’s event.