Cameron Diaz and Benji Madden
It's said to be getting serious fast
. And indeed, Benji Madden seems perfectly thrilled with life since he began dating Cameron Diaz
"I'm really happy right now," Madden told PEOPLE Wednesday at the Alt 98.7 Penthouse Party at Hollywood Tower, where he and twin brother Joel
played an acoustic set of new music.
Asked how his relationship with the actress has affected his music, Benji, 35, said love is indeed a muse for him.
"It's same for any man, no matter what they do. It drives you," he said. "All people, I think, react the same way to the same situations … like we were saying with Joel being a father … we all want to be the best we can be."
Joel admitted, too, that love – he and wife Nicole Richie
have two children together – is a driving influence in his art.
"I think it affects your life, and that affects your music," he said. "Ultimately, my life revolves around my family. Everything I do is for them. I want my family to be happy. And so that has been a life change over the last few years."
The Good Charlotte bandmates, who have been recording lately as the Madden Brothers and have a new album, Greetings from California
, out Sept. 16, played a handful of new songs Wednesday, including the single "We Are Done." All the music is deeply personal and rooted in their new lives, said Joel.
"Musically, it's been three years of an artistic kind of exploration. True exploration," he said. "We're expressing ourselves. This is who we are now. This is where we're at. And this record says everything about our lives now."