Personally, I don't think it's a good way to do things. It's not the way it's done in the pro studios.

A singer has to hear themselves when they sing or they get off pitch pretty quickly. The singer should only hear his/her voice in the headphones in addition to the music. If they need to hear the natural voice, they can lift one of the cups a bit.

If you are recording a vocal, the assumption is that the room is quiet and the singer is getting everything through the cans, and with enough volume to hear everything cleanly.

If, however, you wanted to have the singer NOT hear his voice in the cans, In order to hear the reference music clearly in order to sing with natural voice for reference, the music also has to be in the room loud enough. The mic then picks it up as well as the voice, and you get into phase issues and comb filtering of the music becomes a very real issue. Not counting the possibility of actual feedback and low frequency rumble.

It's best to have the reference music and the singer's voice together in the cans and the room totally quiet except for the singer's voice. Even with this setup, it's not uncommon to get headphone bleed into the sensitive condenser mic that is generally only a few inches away from the cans.

Yeah, bad idea.

You can find my music at:
www.herbhartley.com
Add nothing that adds nothing to the music.
You can make excuses or you can make progress but not both.

The magic you are looking for is in the work you are avoiding.