This is common at nightclubs (or was) - a DJ can use their headphones as a microphone, speaking into one channel and listening to another

Example https://m.youtube.com/watch?v=1NNP6AFkpjs

:-)

You will still see DJs do this in NYC! Old school flavor. You can also see Skepta rapping into a pair on the the music video for That's Not Me: https://www.youtube.com/watch?v=_xQKWnvtg6c

I've seen some theatrical DJs bring a cheap pair, snap them in half, and then use them like a "lollipop." Crowd eats it up. Even older school: using a telephone handset: https://imgur.com/a/1fUghXY