I seem to recall having read over 20 years ago that in saama-veda recitation one of the (usually?) two pandits is intentionally flat, The interference thus created seems to add some special effect, or stuff, to the recitation:
http://www.gypsii.com/place.cgi?op=view&id=4377826 The lyrics are from the first suukta of Rgveda, its 7th verse.
