Ah, so you essentially take the existing stereo mix -> force it to mono -> play the new mono feed in both ears? That's an interesting idea... I feel like this

Ah, so you essentially take the existing stereo mix -> force it to mono -> play the new mono feed in both ears? That's an interesting idea... I feel like this should be relatively easy to replicate with VAC (https://vb-audio.com/Cable/ https://vb-audio.com/Cable/) and Audacity, if the player doesn't support it natively.