A messed up score generally, what with the do-flats in the fourth line, the misplaced key signature in the last line, etc. The C could very well suggest some sort of proportional, metrical approach. Or it could just mark the voice (cantus), perhaps to distinguish this from other polyphonic scores.

Is it possible that the top of the "C", which has a neume-like hook, is a clef marking the "do", and the clef beside it is marking "fa"?

That works for all but the 2nd staff from the bottom... which might be a misprint, or it might indicate something else. Interesting that the symbols are in a different order in the first staff than from all the other staves.

Thanks for the feedback. I like the suggestion of chonak, though if that is true, it is wrong, because then you are marking the "fa" like a "do", and using the "C" then for a "do". Which is messed up. But it does make it more singable, it would be out of the vocal range of most men I am thinking if you take what is properly a mark of the "do" as a "do". Giving the overall quality of the book, a misprint is not unlikely.

The book is a 1893 printing of the Office of the Order of St. Paul the First Hermit. The hymn is in an appendix.

It is difficult to tell what exactly in going on without being able to make comparisons with other parts of the book. E.g: If some pieces have a C at the beginning, and others a 3, then it's obvious that those are mensuration symbols. Do you have access to the whole book, or just this page?

There are only two other hymns in the book (yes I have the whole thing) but neither of them have this symbol, though otherwise they are in the same style.

No idea how to go looking for Polish Chant form the end of the 18 hundreds, or other editions. Well not while I am on the other side of the world from Poland.

Looking at it again... the C symbol cannot be a clef. Although it is always in the same position, the key signature flat symbol is in three different positions throughout. (Not counting when it is used as an accidental).

To Richard's point, I would believe this piece is not chant, but modern notation derived from chant notation. For the notes, it seems that the stem (and perhaps the side the stem is on) may indicate some sense of duration as opposed to notes without a stem.

If the C symbol is not a clef, I also don't understand how it could be connected to a time signature, given the note groupings... but perhaps.

The other symbol - which I would probably take to be the clef... is missing when the clef clearly shifts 3 lines from the bottom. Most curious.

OK this has got a lot more interest and raised a lot more points then I had thought it, would so I am going to attach the whole hymn now, not just the sample, because there are some other oddities in it that might interest a few.

Also the other two versions of the hymn I have in different melodies, if they are useful reference in this discussion.

Also I should note I have not properly checked if I made any transcription errors in the notes, but it is late and it has been a long day. I just wanted to get it up quickly.

It seems to me that the clef sign is an F, which would make the b sign a B-b. The one # sign is to make the B-b a B natural. The 'accidental' b sign makes the E a flat. I think that the 'virgas' are more or less half the value of the plain notes - they seem to move faster following the initial note of a word and the concluding note of a word, sort of like a decorative 'melisma' that moves a little faster than the beginning and ending of words. This treatment is not altogether at odds with the way an amateur or poorly trained singer sings 'chant' or speaks. Also, it was written as it is by a person who had no inkling of what real chant sounds like. As for the 'C', it remains a mystery. It must not be a time signature because nearly every 'bar' has a different number of 'beats'. And, there is that 'bar' for the word ab, which has only one note. I have never encountered the likes of this and am curious as to its solution (if there is one). It is obviously very corrupt chant - if indeed it can be called chant. (Also, one notices that the 'C' follows the F clef in the first line, and precedes it on all following lines - this may or may not be of any significance.)

The standard mensuralist chant practice divides the notes into Longs (square with a stem--"virga"), Breves (square), and Semibreves (diamond), with their normal proportions of 2/1. I haven't looked closely enough at this chant to see if the standard practice holds, though.

Well if it is F clef, what I did at least is partly correct, as I used the Medicaea style F clef when recreating it.