I don't mind when the karaoke host sings....as long as it is not more than the customers
!
If they sing at the beginning of the rotation, I don't see why not....that way, at least you know where it starts and ends....and can kinda figure when you are going to sing next.
Plus, some KJ's sing really well, and I like to hear them when they sing.
Now, if there are like 30 singers..well, then that is up to your judgement.