The violence that erupted during a music festival at Webster Hall in the East Village on Friday night lasted just a few minutes, but apparently it had been brewing for some time.

When it was over, Michael Couls, the bass player of the Cro-Mags, an influential New York hard-core punk band, had been slashed with a knife, and one of the band’s founders, Harley Flanagan, was under arrest after being caught by security, witnesses said.

The attack took place during a show that also featured the bands Sick of It All and Vision of Disorder and was part of the first CBGB Festival, organized by investors who recently bought the assets of the now-defunct music club that stood on the Bowery for more than 30 years before being closed in 2006.

Mr. Flanagan, 45, was the band’s original bassist. On Saturday, he was charged with assault and criminal possession of a weapon.