Typically at the beginning of the psalm the cantor will sing the antiphon once alone, and then the whole congregation will sing it together once at the end of the psalm.

When we sing Evening prayer, I set the Antiphon to the same psalm tone as the psalm. The cantor sings it the first time before the psalm, and everyone sings it after the psalm.
My parish is getting used to this style of vespers and the psalm tones though, so I can probably have everyone sing both iterations of the Antiphon next time.

What Chris describes above is correct, but I cannot conceive of congregations I have worked with singing Gregorian antiphons on one hearing, even with English text. Maybe they’ll learn it after a while if they attend weekly Sunday vespers and the antiphons are the same each week.

Learning the music is how the congregation will be able to sing the antiphons, I don’t see how semidoubling helps in any way. That is even less times for people to hear or practice singing the antiphons.

I know plenty of places where evening prayer from the current Liturgy of the Hours is referred to as Vespers, particularly when it is sung.

I find myself in complete agreement, Chonak, with your strong opinion, but I thought I should alert our OP to the existence of the practice.

I think there used to be a fad in this country of making an artificial distinction between the two. Now that the USCCB's web site says that Vespers and Evening Prayer are two names for the same thing, we don't have to worry about fighting that old error any more.

And to add a bit more fuel to the flames, I will add that in much of the English speaking world we use a different translation of the Liturgia horarum labelled 'The Divine Office'.

Long ago, and for a long time, it was customary (and rubrical) to sing only about half the antiphon at the beginning of the psalm, then chant the psalm, then sing the whole antiphon after the Gloria Patri. This was done on so-called “semidouble” feasts, including ordinary Sundays.

On “double” feasts like today the whole Antiphon was sung before and after.

This was brought to a rubrical end in 1960.

It's tempting to conclude that double feasts are so called because the antiphons are sung twice, but I believe this is false etymology.

Evidently it is more widespread than I had imagined.
I still think it's a bad idea UNLESS there is the practice and intent of differentiating (for example) solemn feasts from (say) 3rd class feasts or Feria, maybe. Still, Count me unconvinced that it's a good idea.

But that's not at all how the term is used anywhere else in the liturgy, even where doubling antiphons was really, really rare (like in the Dominican rite), as the Roman rite is actually really generous in this respect, since, unless it's a feria of Advent or Lent, there's no trace of the ferial office at all. Now, this change might because these things are irrelevant outside of Rome except there are a number of features, like the stational churches, which are also irrelevant, but they nevertheless passed into the Frankish liturgy, and Rome itself entirely abandoned this custom, so one would have to explain how the Lateran passed from the ancient Roman usage to something closer to that of the papal court, all while the term "duplex" completely changed its meaning.

Also, for the hours which existed, the Office of the Dead was a full office, albeit different from the ordinary hours and therefore probably from an earlier period of the Roman rite's history…

I will add my 2 cents: whenever I have sung the office (even publicly) using the pre-55 rubrics as far as calendar/commemorations/ceremony are concerned; we always sang the antiphons twice.

It also depends, I believe, on the antiphon and psalm text. If the antiphon text is the same as the first psalm verse, one of them is cut short at the beginning. I can't remember which.

Right. For example, on Sunday at Vespers following the older rubrics, you only sing "Dixit Dominus" to the antiphon melody, so the jump from "Dixit Dominus" to "Domino meo" is a tad strange at first, but you get used to it, and it's only a third, from Re to Fa. In places that follow 1962, you go to "Donec ponam," and I personally like the custom of the ICRSP to sing the psalm incipit at the beginning of the first verse actually sung to the psalm tone (so you sing Si-La-Do-Re on "Donec").

Even though they don't do the commemorations, the clerics and schola of Saint-Eugène-Sainte-Cécile in parish do not double the antiphons for most of the year (they have done so in Advent for some strange reason, but, and I say this with great respect, the previous pastor, Canon Guelfucci, was a tad idiosyncratic.)

No one who isn't a canon of a handful of churches has permission to use the ancient hymns either, and yet.

Edit: no, SESC does not add the commemorations or suffrages. On Laetare Sunday that would have been of a confessor not a bishop and of a doctor. They went straight to the Benedicamus Domino after the collect.

We did LOTH Vespers here for about six months (Birmingham AL) at St. Paul. We usually did it in English, but (roughly) approximated what they do at the NAC in Rome.

We used the new Antiphonale II, which I actually got very accustomed to and enjoyed, for the antiphons; cantor sang incipit, then all BEFORE the psalm, then everyone in whole after the psalm (Weber tones in alternatim between cantor and congregation). Responsory usually based on the traditional melody, but in English.

I liked it. We didn't differentiate the performance of the antiphon based on the feast, etc., but then the new books don't, and customs don't really exist here regarding the office.