I have been accused of being pedantic in wanting to sing chant from texts in square notation on a four-line stave.
Having been issued with chant transcribed to modern notation, I now realise why this should most definitely not be used, except by the accompanist, who obviously would have difficulties in playing a keyboard instrument from Gregorian notation.
First and foremost, some of the transcriptions are plain wrong. Then there are sloppy changes like writing one double note dotted where the square notation shows three individual notes and should be sunq as three separate notes. Then there are subtle details like liquescents and quilismas which have been ironed out. Added to this are problems when musicians expect to find time signatures where there are none because the rhythm is derived from the words of the text.
So the end result when trying to sing chant from modern notation is that it ends out flat, unmodulated and very boring, thereby helping to put off another generation from ever learning it.
There is nothing difficult about singing from chant in square notation on a four line stave. First you read the words several times to find the rhythm. Then you make sure you know more or less what the meaning is. Then you add the intonation to the words. If you can read music it should be easy, if not, the tune has to be learned by heart which was the traditional way in any case. The way the notes are written show how to form the phrases which give the music its form, which should be reminiscent of waves gently breaking on a beach. If you are conducting, the notes actually show what the hand movements should be.
If you are running a choir singing Gregorian Chant, make sure the singers have the music written in proper notation. If you are in a choir, ask your choirmaster or choirmistress to obtain it. If you have got scores using modern notation for chant, used them to find the tunes from a keyboard, but don't try to sing from them.