The stage was filled nearly to capacity with musicians, fans and their instruments. The crowd was raucous. The lights were bright. As a special birthday treat to Derek Davies, one of the organizers of the Stars & Stripes Festival, the band St. Lucia was going to play their hit single September with the help of Haerts and a full entourage of Derek’s friends. St. Lucia’s frontman Jean-Philip Grobler pressed keys and twisted knobs on his synthesizer, cueing up September’s opening chords. When the bass drum kicked behind him, the crowd began to clap in time with the music.

Held at Flatbread on Saturday night, the festival was a fundraiser for the YMCA of Martha’s Vineyard. It was organized by Neon Gold Records, the boutique record label that Mr. Davies, an Island summer resident, founded with his friend Lizzie Plapinger. The pair first met as kids at the Chilmark Community Center. Now they had decided they wanted to give back to the Island community that had given them so much.

The night began with performances by Vineyard teens Tessa Whitaker and Darby Patterson. Ms. Whitaker stood alone onstage with an acoustic guitar and sang songs she had written herself. Ms. Patterson’s sultry vocals were accompanied by an electric piano. The night was just warming up.

Island favorite Dukes County Love Affair was the first headliner, dishing up their signature blend of hard rock instrumentals and silky lyrics. Frontman Mike Parker two-stepped around the stage, at times breaking out his beat-up bullhorn to lay down key lyrics.

Nicholas Petricca of Walk the Moon got crowd on their feet. — Ray Ewing

Up next was Brooklyn-based lo-fi pop group Haerts, whose ringing guitars and fuzzy synths smoothed out DCLA’s hard edge. The female-fronted band is a little reminiscent of Fleetwood Mac but with a twist of neon. Vocalist Nini Fabi, a modern Stevie Nicks, displayed an impressive knack for belting out sustained vocals without sacrificing her pitch. The dance floor had grown crowded by this time although people were listening, not so much moving.

St. Lucia solved that problem. The crowd roared as Mr. Grobler and his band took the stage, surrounded by synthesizers and guitar effects pedals of all kinds. Their sound, at once electronic and processed, raw and authentic, filled the room — and the dance floor came alive. Catchy synth melodies and powerful vocals drove the crowd wild. With the characteristic swagger of a true rock star, Mr. Grobler sliced away at his guitar and even took a jump from the drum platform.

Finally came the big act of the night with Walk the Moon, an electropop group from Cincinnati, Ohio. Frontman Nicholas Petricca took the stage dressed in an American flag vest and pink and black-striped skinny jeans. If the crowd was tired from its run-in with St. Lucia, it didn’t show, and all were ready to jump around to Walk the Moon’s poppy guitar lines and sing along with catchy choruses. The lead singer wriggled his way around the stage, pausing occasionally to tweak the settings on his synthesizer or pound on a multi-colored drum with sparkling red drumsticks.

And then Stars & Stripes was over and a deafening silence hung in the air. Concertgoers that had trickled in all night poured out the door en masse, tired but satisfied.

The YMCA was also left satisfied as the evening raised a record amount for the organization. Whereas previous years’ festivals raised approximately $30,000 each, this year’s festival netted more than $80,000, all of which will benefit the YMCA.

Next year’s festival takes place on July 5, 2014.