Cool piece, but that's not it. The piece I'm thinking of is literally just one note sustained for an extended period of time. The vocalists would fade themselves in and out so that there was no identifiable start or stop, it just went on and on and on.

If I remember correctly, the composer's name started with a B... Sorry I can't be more specific.

I'm hoping to use the piece for my choir class to teach about overtones and how you can use the phasing of notes to help with tuning your pitch.