I have only read the first page of answers and agree - with thousands of shows under my belt, I have NEVER seen this done, as a band member, audience member, or while I was working as a FOH engineer.
It's a stupid idea for countless reasons I won't bother to get into.
Now before I read the rest, I will make a prediction (perhaps it's been revealed already), your singer wants to do this because he is thinking of the stereo field placement of instruments in a recording. Bass and drums (and vox) up the middle.
I'd bet my fullerton jazz bass on it.
It's a stupid idea for countless reasons I won't bother to get into.
Now before I read the rest, I will make a prediction (perhaps it's been revealed already), your singer wants to do this because he is thinking of the stereo field placement of instruments in a recording. Bass and drums (and vox) up the middle.
I'd bet my fullerton jazz bass on it.