I was really thinking of entering acapella. I can appreciate your position regarding the karaoke-ness of it though.
I may enter in a coming week without accompaniment and if that means I'm disqualified then, so be it =) at least I got myself out there.
There are exceptions so give it a go. Also, there are other contests on Steemit that except Karaoke entries like Pitch Perfect.
You could also find a musician to play with.
Here at Open Mic we want to create a group for musicians who play musical instruments.