That sound you hear on Livin' On A Prayer and It's My Life from Richie - "woh-woh-wooh", etc. They've over used it a bit recently on their latest releases. I don't really know much about it technically but the sound from Richie's guitar amps kinda plays back into his mouth and the shape of the mouth gives that sound. It's then played back through the microphone. If you look at their live vids, it's that straw thing that Richie looks like he's chewing.