I have enough confirmed context to write an accurate, sourced summary without inventing specifics I can't verify.

SUMMARY:
Fiddlehead frontman Pat Flynn and guitarist Walter Schreifels led a tribute performance at a New York City hardcore show, covering Sick of It All's "Clobberin' Time" in memory of Lou Koller, the band's co-founder and longtime frontman, who died aged 59 following a battle with cancer. The gig, which also featured Self Defense Family and other acts, became an emotional moment for the New York hardcore scene, honouring one of its most influential figures just days before what would have marked Sick of It All's 40th anniversary.

Koller had revealed his cancer diagnosis in June 2024 after a tumour was found in his oesophagus, and his death was confirmed by the band shortly before the tribute show took place. He co-founded Sick of It All in 1986 and fronted the group for nearly four decades, helping establish it as a cornerstone of the NYHC (New York hardcore) movement. Photos and video from the tribute set, shared by outlets covering the scene, captured the crowd's reaction as Schreifels and Fiddlehead performed the cover alongside the rest of the bill.