Smartmom and Hepcat had the night off. Sort of. Teen Spirit, as always, was busy with friends and the Oh So Feisty One was iChatting with a camp friend who lives in Massachusetts.

They could have done anything — within reason, of course. They could have gone to the Pavilion to see Oliver Stone’s “W.” or “Burn After Reading.” They could have had dinner at the Stone Park Cafe or gone to Bar Reis for a Scotch.

But no. Smartmom wanted to go to Rock Obama, a benefit show organized by Lily Isadora, a 15-year-old singer-songwriter, with seven local teen bands.

Hepcat was, most decidedly, not in the mood. Napping on the couch, he was in for the night. But Smartmom was jonesing to hang out with a bunch of underaged rockers, who were coming together in support of the next president of the United States. And her son’s band, The Mighty Handful, wasn’t even playing in the show (though, let’s be honest, she knew she’d probably see him there).

“I’m tired,” Hepcat told her. “Besides, we have no business being there.”

Smartmom knew he was right; Hepcat is the sensible one when it comes to giving the kids their own space. Face it, Smartmom really only wanted to go because she knows that in a few years, she’ll have an empty nest — and it already gnaws at her. But of course she didn’t say that to Hepcat. Instead, she made the argument that she really wanted to go to the event because her favorite bands would be playing.

“Radiates! And Calamus! Banzai and Lily Isadora!” she said.

“You’re a groupie,” Hepcat said.

“Yeah, I’m a groupie,” Smartmom concurred. “But it’s for a good cause.”

Hepcat got up from the couch and agreed to come along

When they got to the Lyceum, they ran into their 17-year-old next-door neighbor.

“There are a lot of ninth graders in there,” she said grimacing.

“Ninth graders,” Smartmom whispered. “We really will be the oldest people in the room.”

Once inside, Smartmom and Hepcat were relieved to see some of their middle-aged friends. Lily Isadora’s parents looked exhausted from setting up and chaperoning the crowd. Smartmom’s good friend, Stone House Doyenne was there as was Seaside Diva, who was taking money at the door and stamping hands.

Smartmom went down to the performance space, where kids were moshing to the sounds of Banzai, one of Smartmom’s favorite bands. She couldn’t see a thing and the noise level was oppressive. Then she looked up and noticed that most of the middle-agers were watching the show from the upstairs projection booth (smart kids).

Upstairs it was civilized; the sounds were muted and they had a good view of what was going on below. They even got to sit on comfortable chairs. Good deal. It was like being in a Sky Box at Madison Square Garden and watching a game in style.

Sort of.

Ah yes, the parental booth. Smartmom had a healthy distance on her son who was downstairs enjoying the show.

It gave her a thrill to be able to spy on him — and listen to the bands she is so fond of. Then again, one of his friends told him she was there so he knew he was being spied on.

From her parental Sky Box, Smartmom had a nice overview as she thought about the passage of time. Teen Spirit looked manly wearing his grandfather’s double-breasted suit jacket and black lace-up shoes. He’s even sporting a mustache-less beard these days.

Smartmom saw Teen Spirit’s childhood best friend. They were inseparable when they were students in pre-school, where they promised that they’d always invite each other to their birthday parties. Tall and handsome, he was playing volleyball with a Poland Spring plastic bottle.

Smartmom felt, you guessed it, wistful and sad about the passage of time — but also excited that Teen Spirit and his friends are on the cusp of the rest of their lives.

She wondered if they see it that way. Probably not: they’re so in — and of — their adolescent moment.

By the time she and Hepcat left the Lyceum, Smartmom was glad they’d come. She may be a Brooklyn teen band groupie, but Teen Spirit will graduate from high school next June, his future, as yet, undecided. These are the salad days of his life and Smartmom wants to be around him — even at a distance — as much as she can before he moves on to the next stage of his life.

Whatever that is