[jnorman]

ben maas always provides excellent advice. i would only add one caveat - it is all too easy to get too much reverb on your tracks in a large hall, and there isnt any way to get rid of it once it is there. i would recommend working the mics as close as you can comfortably get to the performers, even if you have to add in a touch of digital verb during post. a nice ORTF pair is certainly a proven approach to this kind of recording, but if it was me, i would likely spot both the singer and piano in case i needed it later (if, as ben notes, you can do it without irritating the vocalist).