Beatboxing with Atmosphere

In an interview with Twin Cities, the Minneapolis band Atmosphere talks about it's new album When Life Gives You Lemons, You Paint That S—- Gold. Apparently Tom Waits beatboxes on one of the songs:

Slug (vocals): ''I'm friends with his son. We've known each other for quite a while now, going on five or six years. And I finally asked him, I think literally, 'Have I known you long enough now to ask if I can get in touch with your dad? Or is that offensive?' So, I sent him the song and asked if he'd sing the chorus. He sent it back and totally avoided the chorus, but instead beatboxed on it. And it sounds good. It worked. We kept it subtle. I didn't want to be exploitive. I wanted to make sure it made sense musically, and I think ultimately it really did."