Lady Gaga closed the FireAid concert in Los Angeles with a live performance of her hit "Shallow" and a brand new song written for the occasion.

After almost six hours of FireAid, Lady Gaga ended the historic Los Angeles event by debuting a new song co-written with her fiance Michael Polansky, an upbeat number that she said was “just for tonight.

The members of No Doubt -- Gwen Stefani, Tom Dumont, Tony Kanal and Adrian Young -- reunited at FireAid Thursday night and sang some of their biggest hits, including "Just a Girl," "Spiderwebs" and "Don't Speak."