For those who are interested, here is a recording of the Persichetti Agnus Dei which we'll be singing on Good Friday:

Unfortunately, this particular choir (the Mendelssohn Club of Philadelphia) doesn't have a very good grasp on some of the chords, but they do get a nice sense of the movement of the piece, especially the tempo changes.

Samples of the remaining movements of this mass can be heard (and MP3s can be purchased) over at Amazon (and probably on iTunes, too).