Next, if you look in the liner notes of the "With a Twist" CD, you'll find this:
No instruments were used in the making of this album. All sounds were produced by voices, vocal percussion, snaps, claps or stomps.So all of those instruments you think you're hearing are actually voices! Organ, saxophone, trumpet, electric guitar, bass, piccolo, drum kit, you name it - all of it is done through their vocals. Even knowing this I still have to concentrate sometimes to hear what sounds like an instrument as a vocal, and I'm always amazed again.
The vocal percussion, or VP, in the group is done by Don, Dave, Tyler, Seggie, Walt and Randy. In his most recent FanChat, Don gives us a brief explanation and demonstration of his VP skills. He can sing two notes and do vocal percussion at the same time!
Now that you know what you're looking for, you can go back and watch some of the videos specifically to see the vocal percussion and instruments. In the video from the Canada tour, you probably noticed Tyler doing VP during Wonderwall. Get Ready is another good one for drums, and so is Billie Jean/Poison. Walt does a "trumpet" in the beginning of Let's Get It On, and there's the Big Band in the Frat Pack Medley. See if you can figure out who's currently doing the jingle bells at the end of 12 Days.
If you're thinking about trying some vocal percussion of your own, Tyler suggests starting out by learning to make one noise while you're breathing in, and another noise while you're breathing out so you can keep a steady rhythm going.
This is just a very basic overview, but I can tell you that the more you listen and watch, the more you'll notice!