This is an interesting find: Basic Gregorian Chant and Sight Reading, by Sr. Maria Demetria, as published by the Gregorian Institute of America (now known as GIA) in 1960. Of all the books on chant to appear in this period, this one is published closest in time to the opening of the Second Vatican Council, at least from what I've seen so far.
I'm curious about these books mainly because I'm interested in just how integral chant was to Catholic culture of the time. My strong impression is that the books that appeared in the 1950s really came out as a "last ditch" effort to save the chant or at least restore the push to the same level it enjoyed in the 1930s before the Second World War pretty well wrecked the stability of American parish life. This flurry of publication were directed toward teaching from the ground up, in the hope of shoring up what was clearly weakening.
This book attempts to explain modern music and then turns to chant by analogy. So there is lots of back and forth between modern notes and four-line staff, keys and modes, modern rhythm and Gajard-style rhythmic theory. This book seems to add an extra element of rhythm theory I had not hear of before: the tallah. This seems to be some pedagogical device to getting singers to give the ictic note an upward movement (the ictus is the lah of tallah) as if the note were thrown into the air.
I tried to read the entire rhythm section with fresh eyes, as a way of evaluating its effectiveness with beginners, but my general impression is that it is extremely confusing and with limited value to the first-time chanter. Especially with the addition of the tallah, it seems like more apparatus than anyone can possibly manage. After all, it is hard enough to sing in a language not your own, sing in a new musical language called solfege, read a four-line staff, learn new rhythm-note combinations, think about word accents, think in terms of arsis-thesis, and then, on top of that, count 2s and 3s and correct the propensity to lean on the ictus by making it an up pulse with yet another pedagogical/language device.
Whew! Chanting is hard but is it really this hard? At some point in all of this, it might be easy to lose a sense of the big picture: the chant is sung prayer, which means that it is more art than machine, more heart than apparatus. It is tempting to look at these very good efforts at pedagogy and gain an insight into why so many were ready to bail out of the whole exercise.
What can the modern chant movement learn from these past attempts? Surely there are lessons here.