Neil and Pegi Young hosted their 25th annual Bridge School Benefit at Mountain View, CA’s Shoreline Amphitheatre over the weekend. The Youngs host the all acoustic, non-profit charity gig at Shoreline Amphitheatre every October and donate all profits to The Bridge School, a progressive non-profit school that aids children with severe speech and physical impairments.

The benefit show’s 25th anniversary lineup boasted a stacked, collaboration-heavy bill that included Neil Young, Dave Matthews, Arcade Fire, Beck, Eddie Vedder, Los Invisibles, featuring Carlos Santana, Cindy Blackman Santana & Guests, Devendra Banhart, Norah Jones with The Little Willies and Mumford & Sons on both Saturday and Sunday. Foo Fighters and Tony Bennett—the latter singer clearly aiming for a new, young audience—also performed on Sunday. Though Late Night host Jimmy Fallon was scheduled to host Saturday’s show, the comedian reportedly missed his flight and was unable to make the benefit.

As is tradition, Young opened both Friday and Saturday’s performances with a solo rendition of “I Am a Child.” He then invited out his wife Pegi for a cover of the Youngbloods’ “Get Together” (his onstage banter also hinted that he’d play the song later in the night).

Throughout his storied career, Neil Young has bridged the gaps between hard rock, folk, country and improvisational music, and he showcased his various personas throughout his numerous sit ins. On both nights, Young joined no less than rising British Americana act Mumford & Sons for his own “Dance, Dance, Dance,” Bridge School benefit alumnus Beck for “Pocahontas” and the duo of Dave Matthews & Tim Reynolds for “Oh! Susanna.” He also sat in with fellow Canadians Arcade Fire for the first time when he emerged partway through their brief set for his sing-along “Helpless” on Saturday night. Though Arcade Fire mixed their setlist up a bit, Young returned on Sunday for a second take on the song (Arcade Fire’s California-born Win Butler dedicated his “Intervention” to the Occupy Movement).

While Young did not sit in with his onetime protégé Eddie Vedder on Saturday, the Pearl Jam frontman did invite out Arcade Fire’s Régine Chassagne onstage to help sing on the 1920s ukulele number “Tonight You Belong to Me” (a song revived by the film The Jerk) as well as fellow alt-rock survivor Beck to help cover The Everly Brothers’ “Sleepless Nights.” After joking that he messed up his Neil Young cover on Saturday night, Vedder finnally invited out the evening’s host to sing on his own “Don’t Cry No Tears” last night. Both Chassagne and Beck also reprised their Saturday sit ins while Marcus Mumford emerged during Dave Matthews & Tim Reynolds’ set for “All Along the Watchtower.”

In other collaborations news, Matthews emerged during a set billed as “Los Invisibles featuring Carlos Santana, Cindy Blackman Santana and Guests” on Sunday for “Love of My Life.” Matthews recorded the song for Santana’s 1999 smash comeback album Supernatural. On Sunday, Foo Fighters’ six-song set surprised fans with Dave Grohl’s solo version of “Everlong.”

Neil Young closed both nights of the benefit with a brief solo set. Saturday’s performance included “Comes A Time,” “Sugar Mountain,” “Long May You Run” and “Heart Of Gold” while Sunday’s set slimmed down to “Long May You Run” and “Heart Of Gold.” On both nights, most of the evening’s performers joined Young at the end of the show for an encore cover of “Get Together.”