Are you talking about a breath controller?
If so, it's a hollow device you blow into which converts air pressure to controller messages. It's loads of fun for sax patches when you use it as a pitch bend controller. Goes all the way back to the DX7.
Or, it could be similar to the old Peter Frampton "Bagman" which was a guitar amp output through a JBL horn driver with a rubber tube attached where the horn usually is. You stick the tube in your mouth and form words and wah wah stuff that is picked up in an ordinary vocal mic. This gimmick was originated in the 50s, I believe, by a guy who billed himself as "Alvino Rey and His Talking Guitar". It was also used to great effect by Rufus (Featuring Shaka Khan) on their # 1 hit, "Tell Me Somethin' Good", and of course Frampton on his "Frampton Comes Alive" album. I don't see why you couldn't use a synth instead of a guitar. I don't know if the "Bagman" is still being made but I think I've seen modern versions in the MF catalog. etc.
If it's really a mic you are talking about I'd like to know what it is too....