Photo by Aaron DeNu

It’s tough not to fixate on whatever Ryan and Hays Holladay are cooking up, so why fight it? After all, a Bluebrain project will probably sound great at its one-off performance and last even longer as an artistic touchstone. Seemingly quiet public dance performances, turning photograph metadata into audio data, scoring the National Museum of Natural History’s Sant Ocean Hall—the Holladays’ output is as full of auditory pleasures as it is “how-the-fuck-did-they-do-that” moments.

Those were the 2010 events. Last year was the year of the location-aware apps, symphonic smartphone programs that guided listeners through some of the country’s great verdant spaces. The first, The National Mall, came out in May, giving a sonic burst of life to our otherwise sodden and trampled front lawn. In October, the Holladays the even more-ambitious Central Park: Listen to the Light, writing 10 hours of music for that green and hilly patch in the center of Manhattan. (I wrote about it for The New York Times, and have also written several articles about Bluebrain for the City Paper.)

But tomorrow’s event gets back to where Bluebrain’s experimental electropop first caught on. The Boombox Walk at the United States Botanic Garden (100 Maryland Avenue SW) brings back a performance the Holladays haven’t rolled out in nearly two years.

They borrowed the idea from the Brooklyn composer Phil Kline, who for years has been composing music that his fans load into cassette decks and tote around New York parks. In September 2009, Bluebrain wrote a 40-minute composition and broke it down into several dozen cassette tracks, each of which was played by a boombox-carrying participant walking around Dupont Circle. The following spring was the big Cherry Blossom Boombox Walk, which featured tracks from collaborators like Chad Clark, Geologist of Animal Collective, Outputmessage and Sockets Records head Sean Peoples.

For tomorrow’s Boombox Walk, it’s just Ryan and Hays composing the tracks. It’s also the last boombox event they plan on staging. Probably ever. (Hey, there are more advanced platforms to work with.)

“I don’t think we ever expected to do another,” Ryan Holladay told me the other day at Big Bear Cafe. “We’ve never claimed this to be our own idea, and we’ve found our own voice since then.”

Still, there’s new novelty to be found even when bringing a chapter of Bluebrain’s body of work to a close. The Dupont and Cherry Blossom walks were outside. The Botanic Garden is much cozier. “It’ll be cool to do one indoors,” Holladay said. It was pretty easy for sound to float off at the previous events, at tomorrow’s, Bluebrain hopes to get an acoustic assist from the garden’s confines.

This time out, the Holladays have composed 20 minutes of new music, which will be broken down into about 50 tracks over four movements. Of course, the trick is making sure everyone hits play at the same time. There will be a countdown at the beginning, but then once the music starts—hopefully in synchronicity—people will be free to wander around, their tracks blending or clashing with others’.

The Cherry Blossom Boombox Walk in April 2010. (Photo by Shauna Alexander)

And then there’s finding people who still own boomboxes. The technology’s just a little ancient, but the Holladays are ready for people who can only muster up CD players or MP3 devices, this admittedly lame iPhone-carrying reporter included. They’ll gladly send a digital track if you email them.

What Bluebrain needs most is lots of people to just show up, ready for an ambulatory musical experience. Being inside, Ryan Holladay likens tomorrow’s Boombox Walk to last September’s “Living House,” when Bluebrain took over the building at 1337 H Street NE and filled each room with its own soundscape, each room’s track flowing into the adjacent space’s.

But, “Living House works with just two people,” he said. “This relies on a critical mass.”

Holladay said to expect lots of “ambient but cool textural stuff” at the Botanic Garden tomorrow. “There’s a piece that’s all acoustic guitar tracks that sounded great in the studio. I have no idea what it will sound like over multiple speakers.”