AR is used for the Roman Rite, AM for the Benedictine usage of the same. The 1934 and 1949 versions of each are used for the 1962 office and the traditional Benedictine office. The Liber Usualis and other books fill in the texts to get one to 1962, but the AR rubrics are official, unless modified by the 1960 changes or another source, e.g. community custom.

I also believe that the AR (and AM too?) for the Novus Ordo are divided into volumes…

No, not as I know, regarding English.

So as I understand it, the "average parish" doing the office in Latin would use the 1949/1960 Antiphonale Romanum, unless they use the 1983 Liber Hymnarius and the 2009 ARii (which are up-to-date?)? Monasteries use the 1934 or 2000's Antiphonale Monasticum, as well as those who want to use it as a resource for alternate chant melodies?

Where can one buy the 1949/1960 Antiphonale Romanum?

graduale:

Are you clear on the difference between, whatever you call them, the Extraordinary Form versus the Ordinary Form?

The Ordinary Form refers to using the current liturgical books, whereas the Extraordinary Form refers to doing things according to the books in effect in 1962. [Both of which are standard & basically universally legitimate.]

Thus:

Extraordinary Form:

If you are a Benedictine: Antiphonale Monasticum (1934)

Examples of Monasteries using this book: Norcia, Le Barroux

If you are secular: Antiphonale Romanum (1949/1960)

Examples of users: say, the FSSP seminary, the Institute of Christ the King, or others devoted to the Extraordinary Form liturgies. In reality, most people would probably be using excerpts from this AR as found in the Liber Usualis, which is an esteemed and very useful anthology, otherwise some other AR-derivative book

Ordinary Form:

If you are a Benedictine: Antiphonale Monasticum (2000's)

Examples: [dunno, actually!]

If you are secular: Antiphonale Romanum II (2009)

Examples: I've seen it used by my diocesan cathedral

[I am not, in fact, much at all familiar with the books for the Ordinary Form office; I'm just taking these titles from your post.]

I might also add, don't refer to the Extraordinary Form merely as "Latin", because Latin is of course normative for the Ordinary Form as well.

Then, for the office, people usually call the EF the "Divine Office", but the OF the "Liturgy of the Hours" (at least, this is the case with the secular versions).

Hope this helps.

Those that have morning prayer or other types of read Office use the LOTH.

If by LOTH you mean the ICEL version published under that title in the USA, then : not in my experience. They use the Collins published version entitled The Divine Office, as authorised in England (and many other countries), with Grail psalms and other translation and detail differences.

@JonathanKK - that really clears things up! I guess I hadn't quite understood that EF/OF applies to the office as well. I was also a bit confused by the lingo...
EF -> Divinum Officium
OF USA -> Liturgy of the Hours
OF UK -> Divine Office ...etc.

By the way - I've come across a nice scan of the 1934 AM (different from what's on CCW).


Graduale