These are two examples made in MuseScore. The Kyrie of the Missa de Angelis and the Graduale of the 17th Sunday after Pentecost.

Greetings.
Thank you, Andrew, for your comment. No. Unfortunately in MuseScore it is not possible to use square notation.

If you want to write music in chant notation, it seems that GABC is the best way to go with a number of tools (mostly free) available.

If you are looking to merge modern and chant, that can be done with graphics in a music program - I typically use Finale, but I would be surprised if most don't have similar capacity.

Attached is an example from Iesu Dulcis (Allen). When I do intonations for polyphonic Masses, I always include the snippet of the intonation in chant as well as the music so one can see the transition of pitch from the intonation to polyphony and understand where it is derived from. Also attached an example of that.

Thanks, Richard, for your corrections.

...is there a way to put and use Gregorian chant notation using Musescore?

@AndrewSteinerPiano So it turns out it is possible to do this. It isn't easy. At all.

Most of the Gregorian note shapes have been included into Unicode. This means that they can be inserted into scores from the Master Palette (Shift+F9). They are, however, just symbols, with no real meaning on the score. It is possible to attach them to notes to get their placement on the stave, but as soon as you're dealing with neumes of more than one note, the task becomes exponentially more difficult.

Attached is a pdf of a score I made. I wanted the Gregorian tone 8g for the odd verses of the Magnificat to pair with a Magnificat Octavi Toni by Lassus. To make it easier to sing the chant at the correct pitch, I decided to attempt writing the Gregorian notation on modern staves, similar to the Weinmann Graduale. The results were actually quite satisfactory, but this was largely because the chant was simple, and once I had the handful of necessary neumes placed once, I could copy and paste them as often as needed. The forum software won't allow me to upload the .mscz file, so it is available on Google Drive here.

I have also attached the finished product for those who may want it - I stole a score for the Lassus from CPDL, broke apart the pdf, and interpolated the chant verses I created.

No disrespect to the OP, but can I politely suggest to NOT use stemmed 8th notes when transcribing to modern notation? Simple stemless heads with slurs are much easier to read. 8th note notation was the fashion many years ago however it is difficult to read and seems mostly spurned by modern publications that adapt chant.

CGM, I agree that long melismas require attention from an engraver, however if they are done well and placed into their proper groupings somewhat akin to how the nuemes are shaped themselves, they are easier to read. (I suppose I should edit in here: a lot easier for me to read anyway.) 8th stems all over the place, especially when you have one stem per syllable make the rest of the chant a bear to read.

I'll also add that individual stemming is frowned upon by engravers for regular vocal music too. Elain Gould talks about this specifically in the "bible" Behind Bars. So it doesn't make any sense to me to use an old convention that is increasingly considered anathema by professional publishing houses for chant.

Stemmed vs stemless is a taste thing. The benefit to stemmed is that it translates into metrical value, with some indication of motion. It’s sort of old solesmes, but the in my experience the stemless notation lends itself to a vagueness of interpretation by musicians not trained in chant. They wander and give it no forward motion.

I don't know... but that's a pretty standard example of what I encounter whenever there's stemmed notation.

Davido, what you laud (rhythm indication) is precisely one of the things that detracts from the merits of stemmed notation... chant is supposed to follow the rhythm of speech, not be sung mathematically. Now of course, we've all been trained to some extent to put particular inflections on certain neumes thereby creating a "standard" rhythm, but by the same token, if you use the mathematical approach with stems I doubt your chant will have much flow at all.

If you can decipher a triple pulse from three notes beamed together, I can't fathom why you couldn't decipher that with three stemless grouped and slurred.

I concede that there's a certain element of visual taste at play here, but I do think the stemmed notes really lay a difficult trap for people who don't know chant very well. It's inevitable that habits from modern music will sink in.

Stemless notation. on the other hand, immediately indicates that there are different rules from 'normal' but those rules are still easily inferred. (notes with dots or white notes are longer, slurred groups are sung together, etc. etc.) I'll also note that stemless notes are actually quite a bit closer to the original neumes themselves.

At any rate, I don't think I'm winning any converts here, and we will all do whatever we esteem best for our choirs. Singing chant, no matter how it's transcribed, is the important part.

Edit: one other general thought for anyone finding this thread in the future: I don't understand why some modern editions of chant forgo the hierarchical nature of gregorian barlines, most of which are easily represented in modern notation programs. They reveal more data. I very much prefer to represent the original barlines unaltered insofar as is possible in my program of choice, and then as my choir grows, I reveal new aspects about how the music is transcribed layer by layer, barlines being one of them.

The benefit to stemmed is that it translates into metrical value, with some indication of motion.

Agree. I don't use the old-school "you can't beam notes together unless they're melismas" approach (e.g. Serviam's first example above), but instead beam the notes of the chant melody in 2's and 3's, to match the way that chant is frequently explained to singers — "the melody flows in irregular groupings of 2's and 3's, which are reflected in the beaming."

Singing chant, no matter how it's transcribed, is the important part.

Agree even more!

m_r_taylor, a LaTeX document can invoke both Lilypond and Gregorio, so it could contain a mix of modern and square-note scores.

@chonak I hadn't considered it, but it can certainly be very useful.

https://musescore.org/en/handbook/lyrics#melisma