St Gall signs can be seen here
http://gregor-und-taube.de/E.33_Of._De_profundis.pdf
looking at the old neums I think you did quite well.

Thanks, BGP, for the link to Anton Stingl's site, a great resource. By the way, could you identify for me which square-note edition he is using in those pdfs?

Good afternoon,
Made it into a single page, easier to handle:
http://www.gregorianbooks.com/img/book/00/of.de_profundis.png
http://www.gregorianbooks.com/img/book/00/of.de_profundis.pdf

So we sang it at mass this morning. It was not too bad. :-)
I did not ask for feedback from the congregation; must have been strange for them to hear something longer than what is written in their missal.

By the way: I forgot a dot at the porrectus of the second profundis in the PDF. Sorry for that. It is fixed now. You may have seen it, the second occurrence of the phrase should be the same as the first one.

Avant-propos: yep, good choice to sing the psalm tone verses from Mr Rice's book.
We could not sing the Requiem Mass (church unavailable for a sung mass) so we only sung two masses this weekend. But I can imagine the tiredness.

@David Sullivan: Let's see...

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There is a lot about understanding how a Gregorian chant melody flows. There is the binary/ternary rhythm, a bit like a waltz but flexible/supple, chant has no beat, there is the alternance of simple notes/lengthened notes, sometimes you emphasize a note with a distropha/episema/dot then you carry on. A lot is based on the experience of Gregorian melodies, remembering the visual aspect of neumes. That's not so difficult. But let's see a few neumes in detail:

- First of all there is often a dot at the end of a phrase, before a bar; here it is even more evident with the few double-dotted clivis ED: I was inspired by the Vir erat from 21st Sunday, same mode 2 and you find a lot of these double-dot endings.
- The "Si" from "Si iniquitates" ends on AGA: there is a similar pattern on "quis" which has a distropha on A when "Si" has only one note, so... you double it. Now look at those two sentences: 1) "Si iniquitates": you must separate the two "i" to hear the two words and 2) "quis sustinebit": you must separate the two "s" to hear the two words. In both cases a lengthened note helps for the transition to the next word: when you sing a lengthened note you tend to slightly fade out at the end, giving a brief silence and impulse to the next word.
- There a few fourth down DA followed by CDF (servi tui, observaveris): classic pattern, heard for example at the Graduale Timete at All Saints, so you lengthen both notes. Here I've put an episema on D, I could have put a dot instead. Never mind.
- An inspiration on the torculus in oratio: it sounds so much better with an episema, doesn't it?... as long as you remember to sing an episemed torculus like this: lengthen the first note, not so much the second one but emphasize it, then not at all the third one which brings you back into the rhythm of the melody. Also remember to sing "in orati-" without lengthening, the lengthening is on the torculus.
- Episema on "fiant": to prepare for the jump a fourth up. Yeah, sometimes you prepare a jump two notes before.
- Episema on "aures": to give time to pronounce the "u", otherwise it sounds like "ares".
- Episema on "intendentes": slight pause here otherwise it goes too quick. Plus it is on the accented vowel. And it prepares for the going down a fourth.
- Episema at the last "Domine": raising high the plea to God.
- Needless to say it was easy for the antiphon: the rhythmic signs exist.

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There is an Offertoriale Triplex from Solesmes, first published in 1964, latest edition 1985. It has the manuscripts old neumes and is similar to the 1966 Graduale Neumé, ancestor of the Graduale Triplex. I do not have the Offertoriale Triplex, never seen it, so I could not analyze the neumes; besides I am not an expert on the old neumes. :-)
A few comments above in this discussion there is Mr BGP who mentioned the work of Gregor und Taube: PDFs where the Gregorian melodies come with square notes and St Gall neumes. I think it is the recent German work which gave the Graduale Novum with slightly different melodies, but at least you can have a look at it for the old neumes.

In the end these rhythmic signs are here to make the members of a choir sing together, agreeing on the rhythm. As long as you keep the melody correct you can interpret it the way you want.
Now when the monks from Solesmes worked on restoring Gregorian chant they did not only publish their theory but also taught/performed for choirs around Europe. These choirs would quickly admit that the way the Solesmes monks were singing was the right way because it sounded good and inspired. The best way of interpreting a Gregorian melody naturally emerges and finds the recognition of everyone.

I made a pre-recording, at home quietly, gave it to my choir:
http://www.gregorianbooks.com/p.php?p=MPjp/of.de_profundis__verses.mp3,00/of.de_profundis.png Starts on pitch C#.
Be gentle please, I am not a professional singer, this is much more for didactic learning. :-)

I wanted to challenge my singers a little bit, bringing some novelty to avoid monotony. And this is such a beautiful and striking Offertory. Psalm 129, one of the 7 penitential psalms. Pfff !

You can bring suggestions on how you would interpret the rhythm.
There are 3 other opportunities, "23rd Sunday", to sing it.

Well... I learned a new English word today: "dirge". :-)

Source Wikipedia: from the Latin "Dirige", first word of the first antiphon (Ps. 5, 9) at matins in the office for the dead. Dirige, Domine, Deus meus, in conspectu tuo viam meam ("Direct my way in your sight, O Lord my God").

I'll be likely using this as well this weekend.