Regina Spektor isn't a larger-than-life rock star by any means, but you wouldn't know it based on fans' reactions to her sold-out show Saturday night at the Chicago Theatre. Between every song, audience members -- a large number of whom were teen and tween girls -- went nuts, screaming, whistling and yelling things like "I love you!" No, the bookish New-York-via-Russia songstress didn't pull any party-starting theatrics during the gig -- unlike Bono, who was parading around nearby at Soldier Field -- but she may as well have. The vibe was Beatlemania at a symphony.

After Spektor joked that her set list indicated she was supposed to play 'On the Patio' (referring to her 2006 hit 'On the Radio'), someone on the balcony let out an incredibly loud shriek, startling the singer. Handling the situation with tact -- and not displaying a bit of annoyance, a reaction that wouldn't have been too unreasonable given the sit-down audience -- Spektor took a breath and asked, smiling, "Who done it on the balcony...with a drumstick," noting the yell sounded like someone had just been stabbed. What a sport.

Not to be outdone, Spektor lightened the mood even more by ending with a rousing encore of 'Hotel Song,' a dreamy tale involving sex, cocaine, whales and owls. For the first time, she paced in front of her band without an instrument, bobbing her head like a rapper. Then she flubbed a line and unabashedly said "F---!" and laughed. Young'uns -- and everyone else in attendance -- cheered. Which, come to think of it, is pretty rock 'n' roll.