Minimal effort taken to the max

Near the end of the Raveon- ettes’ sold-out Tuesday show at the Troubadour, glamazon singer-bassist Sharin Foo explained that the Danish duo writes songs in only one key (B-flat minor), uses three chords and won’t allow tunes to last longer than three minutes.

The 6-foot blond and her equally rangy partner, singer, songwriter and guitarist Sune Rose Wagner, wrung surprising variety from these self-imposed restrictions. Then again, a lot more went into their music than their minimalist approach might have indicated.

Abetted by an additional guitarist and a drummer, the pair bookended the 50-minute set with a super-distorted take on Buddy Holly and Norman Petty’s classic “Everyday” that nevertheless kept the melody recognizable. Foo’s bass line set a dirge-like pace, while the duo’s muffled boy-girl harmonies barely crested cascading waves of sustained, almost pretty guitar noise recalling the Jesus and Mary Chain.

The decadent, jagged-to-sweet selections from the eight-song debut CD, “Whip It On,” reflected Wagner’s brief residency in the U.S. Emulating Jack Kerouac’s impromptu musings, his stark lyrics took a dark look at Vegas in “Bowels of the Beast” and celebrated defiant desert driving in “Cops on Our Tail.”

There was a whiff of Sonic Youth artiness, but the music also evoked a twisted Wall of Sound, the Velvet Underground and such punk influences as the Cramps. Despite the calculations behind it, it remained authentically in the moment, as spontaneous and apocalyptic as rock ‘n’ roll should be.