Holed up with a line of bizarre instruments in an old rural mansion in upstate New York — instead of the urban apartment that birthed most of their past successes — Mike Stroud and Evan Mast laid down the tracks for their sixth album in as many years. The departure from such a winning protocol may have been risky, but given the indie duo’s love of exploration, a shift from routine was in the cards.

The electro-rockers typically trade out standard vocals for such oddities as bird chirps, wildcat screams and German voiceovers — a trend that continues throughout LP4. The pair devised the album during the same recording sessions that wrought LP3 two years ago; they divided the tracks between the former and its brand-new sibling.

While its title is a decidedly lateral move, LP4 expounds on the otherworldly aesthetic honed on LP3 — weaving an unfamiliar body of global exoticism into LP3’s clean-cut sound. The latest incorporates a tribal backbeat and — for the first time — a full string section, building upon the vanilla-synth lightness of its 2008 predecessor.

An excess of dicing, reversing and layering makes it difficult to discern which instruments are responsible for the group’s new Eastern twang. However, the notable reintroduction of Stroud’s heavy guitar rifts — in contrast to the rock-starved LP3 — is a welcome return to the sound of early albums “Ratatat” and “Classics.”

“Sunblocks” typifies the duo’s new vamp: A tinkering melody builds into a thunderous wail. Tracks “Drugs” and “Party with Children” have a similar effect — shifting from lurching, eerily sober beginnings to full-bodied electronic symphonies.

Sure, LP4 is technically a cheat: The title practically owns up to the fact that these are the dregs of 2008. But that’s precisely what makes LP4 great. Its self-contained identity somehow manages to encapsulate vintage Ratatat without collapsing into a creative rut.