As I interpret them, the authentic melodies *are* rhythmic.

AP23, I remember a setting of the Veni Sancte in the Ritualsong hymnal that put the original chant in 3/4 . . . a "rhythmic" setting, if you will. It was edited by the late Richard Proulx, IIRC. Search over at the GIA site and you may find it.

Chant with mensuralist rhythms is still chant, is it not? The version of the Veni sancte spiritus tune in question is taken from the Dublin Troper, ca. 1360, and is certainly valid. Both the versions arranged by Richard Proulx (published by GIA - search on their website) and the version in the Worship hymnal use a translation by Peter J. Scagnelli. As I understand it, we are not obligated to use the official translation anyway for this. However, provided that the poetic meter is the same, as it should be, you could certainly substitute that translation in any sources you find. I am not aware of any such version of the Corpus Christi sequence.

Chant with mensuralist rhythms is still chant, is it not?

Precisely; "rhythmic settings" and "chants" are not mutually exclusive categories.

Could you please give me a link to previews of these "authentic melodies"?

Sure, but indulge me in a little autobiography first: my jazz-loving father had only one LP of sacred music at home, and it happened to be a recording of Gregorian chant by Cappella Antiqua Muenchen, directed by the late Konrad Ruhland, so I was exposed at a formative age to Ruhland's interpretation of the chant. He worked from the assumption that metrical texts (e.g. Office Hymns & the later sequences) would have been set to mensural melodies - tunes with a regular "pulse" or beat that could, if necessary, be written out with bar lines. The sequences, in particular, seem suited to triple time. This is why Ruhland's recordings sound like this and this. Now his particular interpretation may sound better at an early music festival than at Sunday Mass, but the basic principle can be applied in liturgical performance with (I think) very pleasing results. It may also be worth listening, for comparison, to the way Paul Hillier sings "Ex te lux oritur", a secular wedding song but one whose text is metrically akin to the sequences we're talking about, and whose music is written in square notation in the MS. Even more telling is Paul Rendall's performance, which for the first two minutes resembles an equalist perfomance of chant (i.e. giving each note an approximately equal time value). After two minutes, it bursts into a much livelier rhythm. Compare & contrast.

This may not be quite what you have in mind; here in the UK the Pentecost Sequence is often sung to a 777D hymn tune by Samuel Webbe. The tune is called "Veni Sancte Spiritus" and sounds like this.

[comment edited to remove slightly snarky tone!]

This is a perfect example of a forum topic that gets hijacked for the sake of screeds, and why I don't choose to participate much. Obviously, the question was about metrical settings of Sequences, which you may or may not appreciate, but have no right despising either. I wonder how many good Catholic musicians are totally turned off to CMAA by this type of chatter. I know I am.

Ben:

Ruhland's "particular interpretation may sound better at an early music festival than at Sunday Mass,"

Ruhland certainly did not view his interpretation as an "early music" one, as opposed to a liturgical one. I spent a year in Munich in the 60s, and Ruhland's Capella Antiqua sang for a Mass once a month in a church in Munich, singing Gregorian propers and Medieval and Renaissance ordinaries (Josquin, Lasso, Machaut, Ciconia, etc.), as well as giving a seasonal concert. The performances did not differ. Moreover, they were very effective liturgically. I came home from that year, and began to introduce Renaissance ordinaries on occasion, though I don't sing the sequences metrically.