Well they have both the music-speech (mic) and the pure music signals inside the empeg, so if they have problems here and want to be REALLY tricky they can subtract the music signal from the microphone input and end up with just the speech (+ engine noise etc.). Anything is possible

(list 6284, Mk1 S/N 00299 4GB blue [for sale]. Mk2 S/N 080000094 6GB blue)