When the world is your instrument, everything becomes music. Consider: This year, facing the destruction of their longtime London studio and shared flat, Carim Clasmann and Galia Durant spent hours recording the creak of the floorboards and the dry electricity of the carpet. They knocked on the hollow spaces in the walls; they stomped up the staircase.
Later, the duo -- together, they are the pop band Psapp (pronounced ``sap" ) -- wove the sounds into a requiem for the space they were leaving behind and called it ``Upstairs." The song had parts for horn and Durant's voice, but also for the flat itself.
``I'm so in love with that kind of melancholy," Durant said in a phone interview from a tour stop in Oregon. ``You know -- when you hear something and it reminds you of certain people or places that are never going to be the same again."
Durant and Clasmann, who arrive in Boston on Wednesday for a sold-out show at the Museum of Fine Arts, have carved a career out of this cluttered wistfulness: Psapp put ``Upstairs" on its latest disc, ``The Only Thing I Ever Wanted." Older songs like ``Cosy in the Rocket," the theme to the ABC drama ``Grey's Anatomy," are alive with a clinking, clanking physicality.
``Spaces are important to us. Places. Things," Clasmann says. ``It's very important to give everything a sonic belonging."
In the annals of indie pop -- a sprawling, inventive genre in its own right -- Clasmann and Durant are strangers, if not exactly outcasts. Their music straddles the divide between art rock, which can be willfully challenging, and pop convention, which needs a certain accessibility. The former, as the pair sees it, requires doses of the latter to be commercially viable, and the latter benefits from the thematic curiosity of the former.
``There are different ways to listen to our music," Clasmann says. ``When I play the CD, for instance, I hear two different songs for every track."
On ``The Only Thing I Ever Wanted," which Psapp recorded for the London label Domino Records, this duality is its own reward. The album succeeds almost despite its eclectic instrumentation: Gravel from a path near the Thames, broken toy keyboards, the ping of empty bottles, and cats' meows are strung out over spare, elegiac pop.
Clasmann and Durant first met in London in 2001, after being introduced by a mutual friend. Clasmann was a producer who loved experimenting with sound. Durant had a good record collection and a better taste in music. Their musical courtship was sudden -- by 2003, they had a name, Psapp, and enough material for an EP, ``Do Something Wrong," that foreshadowed the messy sonic landscapes the band would later visit.
But it wasn't until 2004 that Psapp caught its first, unlikely break. That year, Alexandra Patsatvas, who supervises the musical scores for television programs like ``The O.C.," was mailed a CD that included a twee-tinged Psapp track called ``Cosy in the Rocket." Patsatvas was certain that she knew where ``Rocket" would fit best: as the theme song for a promising pilot called ``Grey's Anatomy."
``[Creator] Shonda Rhimes and [executive producer] Betsy Beers really loved `Cosy in the Rocket,' " Patsatvas said on the phone from her California office. ``When we started to focus on finding a theme, this is the track that we returned to over and over."
Psapp is something of an incongruous fit for prime-time TV, which often favors bland or unobtrusive scores. Patsatvas, though, said she thought Clasmann and Durant's music worked for ``Grey's" -- and ``The O.C." and ``Nip/Tuck," on which Psapp has also been featured -- for the same reason it works on the band's albums.
``It's an approachable sound," she said. ``There's also a lot there."
``If I was listening to Psapp I'd hear the sounds first, yes," Durant says. ``But it would be the songs that would stay with me."
The challenge now is translating those songs -- which are, at essence, headphone music -- into a live set. Sans laptops and samples and glass bottles full of pebbles, what will Psapp sound like on an open stage? This is not a Jack and Meg White situation: Clasmann and Durant say they thrive within the confines of their creative relationship, but the translation will be one of adaptation, not replication.
``It's inevitable that we'll lose something live," Durant says, adding that she and Clasmann have had their hands full making their music work with a six-piece band. ``We wanted something louder, enthusiastic," she added. ``It's like we're discovering something new. Again."