Did you ever realize that "Physical," Olivia Newton-John's schlocky 1981 hit and soundtrack to aerobics videos the world over, had a low-fi blues-rock hook trapped inside of it, yearning to break free? Swallows did. So they went to work, let the groove loose, and released an astonishing cover version on their "Physical" single back in 2004.

Truth be told, it's not really a cover; it's more like an intervention followed by heavy-duty rehab. Guitarist/vocalist Em Brownlowe and drummer Jon Miller take the song apart, throw away all but its most essential elements, and rebuild it again on top of a clean drumbeat, suggestive whispers, and some choice guitar noodling. Sung in Brownlowe's alto croon, even the famously terrible lyric "Let me hear your body talk" sounds somehow sexy.

The "Physical" makeover is a perfect introduction to the quirky musical logic behind Swallows. The inventive, ambitious, and adorable duo connected via Chainsaw Records' online message board after moving to Portland in the summer of 2003. They released a handful of EPs and singles, including the EP Physical, before digging in their heels for last year's Me with Trees Towering, their first proper full-length and a solidification of their style to date.

After a label jump from Cherchez la Femme to Church of Girl Records, Swallows are back this year with new material in the form of the Cloud Machines EP. Andrew Roberts' beautiful cover artwork shows two swallow-like birds flying across a crumbling urban streetscape, with a factory streaming brown smoke in the distance.

Cloud Machines' second song, "When You're in Love," falls a bit flat (sample lyric: "'Cause when you're in love/nothing else matters/Yeah, when you're in love/you smell the flowers"). But Miller and Brownlowe are in fine form elsewhere, particularly "Twilight's Last Hour," in which Brownlowe gets a chance to show off her formidable 16th-note-shredding axe skills. "Everyone on Trial" and "Language Is Restless" offer more riffage, plus richer vocals and a political subtext. They showcase a band coming into its own, capitalizing on its potential, and—dare I say it?—getting physical. Ms. Newton-John would surely approve.