In my upcoming job, there is an expectation that Gregorian chant will be used often during the mass (Thank God!). As exciting as it is to be in a place where this is already established and I don't have to ruffle feathers by introducing chant here and there, I must say it has brought the question of interpretation to my attention.
Now I'm no chant scholar by any means but I've been a part of a couple of schola's that have sung chant often, so I am quite familiar with the basics and the "usual" method of chant interpretation. But I'm also aware that there are disagreements in the scholarly community about historical performance practice pertaining to this genre of music, though I'm not well-read on the subject.
One experience I can bring to the conversation though is a service I was a part of with an ensemble in which I currently participate. In was an Advent service in a local monastery with a group of monks who alternated chant with our choral selections. Lovely service to say the least. Anyways, I must say I was taken aback by one of the monks who sang some solo chant. He sang a few pieces in which he took the written line and improvised upon it with a style reminiscent of a heavily ornamented chorale prelude of Bach. Lots and lots of extra notes in a very rapid manner; the opposite of what you expect chant to be.
I wish you were all here in my study so I could vocal-model a bit of it for you, but I will just say that I was completely turned off by it. The armchair musicologist in me found it intriguing for historical reasons, but for spiritual ones, I found it lacking.
Maybe it would grow on me in time, though I doubt it. I must say that I like my chant like I like my beer: smooth, with a nice aftertaste. Give me that meditative, no vibrato, Solesmes-sound any day of the week over Joe Scholar's latest historical interpretation.
Now don't think I'm opposed to the historically-informed performance practice movement. I love my Bach recordings by Gardiner and Parrott among others. I love the sound of those period instruments, the brisk tempos, the clean sound from the choir, etc. But I think it's important to know your audience; people in the pews in Sunday are uninterested in matters such as these when it comes to music. They want to be inspired by the chant and have their hearts "lifted up." I don't feel that the previous example I brought up does the job that is required of the music.
So to conclude, unless I am convinced otherwise, I think it's safe to say that I'll stick pretty closely to the traditional interpretation of the Ordinaries and the Propers with my future choir. In other words, don't expect me to drop some coin for a copy of the Graduale Triplex anytime soon.