A microphone with two separate transducing systems, built into one housing. The two outputs are kept separate, and are fed to two separate tracks on the tape recorder.
"Thanks so much for converting my 42-year old Bar Mitzvah audio-tape to CDs. For such a solemn occasion, I couldn't stop laughing! Hearing my high-pitched, Texas-twanged Hebrew is such a treat; I would never have recognized that the boy on that tape is me. Surely my parents and sons will get a kick out of hearing this voice from my past."