DAVE GROHL Plays New Song 'The Sky Is a Neighborhood' At ACOUSTIC-4-A-CURE IV (Video)

Dave Grohl played a new song during last night's (Monday, May 15) Acoustic-4-A-Cure IV concert at The Fillmore in San Francisco, California.

The former NIRVANA drummer, who was backed by FOO FIGHTERS' Taylor Hawkins and longtime collaborator Rami Jaffee, was filling in for event co-organizer James Hetfield (METALLICA),who was away on tour.

Grohl told the crowd that he decided to debut the track earlier that day. "I figured on the way up here, I thought we would play a new song," he said. "We've never played this before to anybody."

It is unclear if the song — which is apparently titled "The Sky Is a Neighborhood" — will appear on FOO FIGHTERS' next album or be made available through a separate Grohl-related project.

In its fourth year, Acoustic-4-A-Cure features legendary artists performing acoustic sets, epic collaborations and impromptu jams from the stages of intimate and storied San Francisco venues like The Fillmore. The benefit was created by Bay Area rock legends Sammy Hagar and James Hetfield, whose vision was to raise needed funds and awareness for the pediatric cancer research by throwing a must-see concert for fans and donating all of the proceeds to UCSF Benioff Children's Hospital.

FOO FIGHTERS broke a year-plus hiatus in February with a surprise U.K. club show to celebrate their confirmation as headliners for this year's Glastonbury Festival.

The show was the first official FOO FIGHTERS gig since November 2015, although Grohl has done a few low-key solo appearances and the band played at benefit events last October and in February.

A string of European dates in the summer have also been announced, along with one U.S. festival appearance in California, but the FOO FIGHTERS have yet to announce plans for a new album.