Just like Apple Music Sing, it would be great to have a slider to adjust how much vocals are heard in the music. This could be possible to achieve the desired effect matching an ‘instrumental’ track or ‘canceling the center’.
There’s a somewhat related suggestion for Plex to support actual Karaoke formats. If I understand your suggestion correctly, you want Plex to identify/auto-detect and tune out the vocals?
Yes you’re right.
I noticed there are existing discussions about Plex supporting cdg format, but my starting point was just to match 2 audio files in the library that one was the original music containing vocal and background music, while another just containing a background music (track name containing “Instrumental”/“off vocal”). This is very common to see in some Japanese single releases. By playing both tracks in the background in sync and adjusting the volume of both, we could have an similar effect to the Apple Music Sing function.
For the track that only containing an original music, an old simple method of “canceling center” could attempt to remove vocal. Or it could be further achievable by the current AI techie?
My starting point was to have the features on Plexamp since I found myself love to sing along with the song while using Plexamp 
Maybe it would be a better suggestion to also support it on Plex?
