When musicians play San Diego’s distinguished Copley Symphony Hall, they usually don’t get bras thrown at them. It’s hard to imagine, say, Yo-Yo Ma getting pelted with ladies’ foundation garments during a set. But that’s exactly what happened when Canadian super twins Tegan and Sara played Copley on Wednesday night.

A symphony hall is an odd choice of venue for the indie pop duo, best known for the guitar-driven hit “Walking With a Ghost”. But the bourgeois setting and steep prices didn’t stop fans from packing the place. The mostly female crowd greeted the duo with a level of amorous, shrieking intensity once reserved for The Beatles, and it wasn’t long before the band was dodging the throng’s thongs.

The sisters began the set with a block from their most recent album, Sainthood. Songs like “The Ocean”, “On Directing” and “Hell” showcased Tegan and Sara’s urgent, precocious harmonies, and the backing band performed like a well-oiled machine. Unfortunately, the group’s professionalism was marred by an off-balance mix that left the vocals and all three guitars drowned out by loud, sludgy bass. The resulting sound resembled something you might hear blasting from the speakers of a passing car, not what you’d expect from a night at the symphony.

The sound problems plagued the band all night, but the crowd didn’t even notice. The fans loved Tegan and Sara so much they wouldn’t even listen to them, opting instead to scream over the shy, polite duo between and even during the songs. Though clearly accustomed to extreme fanaticism—the sisters joked that they are in the process of constructing a quilt from all the padded bras that have been hurled at them during shows—they eventually ran out of patience for the antics, and took to alternately berating the crowd and pleading with them to shut up.

Tegan and Sara’s music is charming and catchy, floating somewhere between college rock and Top 40 pop, but after a while a sameness becomes apparent. The brief songs rush through perfunctory verses on their way to catchy chorus payoffs, but the driving, monotonous guitar and basic melodies lack the variety needed to sustain interest for a twenty-song set.

The sound and variety problems were simultaneously solved by the sisters’ encore. Tegan and Sara returned to the stage without their backing band, and the reprieve from the excessive low end allowed their musical prowess to finally shine. With just an acoustic guitar and xylophone, the duo launched into a captivating version of “You Wouldn’t Like Me”—from their 2004 breakthrough So Jealous—that showed off the emotional marksmanship that has earned them their devoted following. Finally free of obstruction, Tegan and Sara’s revealing songwriting and tender delivery came together in a moment of quiet, captivating beauty.

Then the bras began to fly again.