For context, image 1 is where I found this tune in another hymnal, and it looks like a sort of free-flowing attempt at notating (in standard notation) how a choir or congregation would sing. Images 2 and 3 are the same tune in the Yattendon hymnal.
In listening to music of this type, and reading as best I can what is given here in image 2, I would expect to hear something very close to image 1. However, I am confused at how the editor came to the conclusion to notate the way he did in image 3, as it seems at odds with image 1.
So, in short: for s as short and l as long, why notate it roughly as sssssssl ' sssssssl in the one case, but llllllsl ' llllllsl in the other?
There is an explanation of sorts in the back of the hymnal, but it is quite long. It is quoted here. I believe I understood most of the explanation, but what I don't understand is why it's translated to the kind of rhythm shown in image 3.
Tune,—assigned in most of the choral books, from 12th cent. onwards, to the hymn at Lauds on Sundays, Aeterne rerum Conditor; and in many to the hymns on Ferias also, of which Splendor Paternae is one. It is found in the Sarum & Hereford antiphoners, but not in those of York. It is not set to either of these hymns in the Ambrosian books. [P.] About the date of these early plain-song melodies there is much uncertainty. There is very great probability that some of them are as old as the words: and we may be singing now the very notes which ravished the ears of S. Augustin in the Milan basilica in the year 386. But in the absence of contemporary musical record, one must regretfully admit the untrustworthy nature of the oral tradition of music, which is subject to constant modification by the singers, in accordance with prevailing fashion. Hence, though the age of a plain-song melody may be judged in some measure by its intrinsic character, experts are chary of committing themselves to any decided opinion. Being thus reduced to the external evidence, the facts are, as far as I can gather, much as follows. The old latin breviaries of the western church contained a cycle of hymns for the year. These breviaries varied in minor details, according to local use, such as the saints chosen for commemoration; and the hymns varied: but all the various hymn-cycles had a common nucleus, which was formed between the first general introduction of hymns, due to the influence of the rule of S. Benedict, about the 6th century, and the liturgical expansion of the 10th century: and there can be little doubt that the melodies had a corresponding variation, though there is not the same early MS. authority for the music as there is for the words. Little more, therefore, can be safely affirmed than this, namely, that when a melody is found in the old books in connection with only one hymn, and in use over a wide area, then it is almost certainly the original melody of that hymn, or an altered form of it (the absence of local modification being of great value), and it may be as old as the words. With less of such evidence, there is of course less probability of antiquity.
The Sarum Hymnal, which was the one in most general use in England, draws the greater part, both of its hymns and melodies, from the common storehouse; but in some instances the melodies have forms which are peculiar to this use. These are of extreme interest; for if they should not be of more ancient authority than others, their form must be the expression of national musical taste at a time when there is little other record of it; and to which it may be said that they do great credit, and for that reason should be jealously guarded from the invasion of foreign and inferior forms. Most of the plain-song melodies in this book are therefore taken from the old Sarum version, the text being that of the Rev. W. H. Frere’s ‘Hymn Melodies and Sequences,’ &c., Plain-song and Mediaeval Musical Society, 1896.
In order to write out for singers a part-setting of a plain-song melody, one must either use the modern notation with its significance of strict time-values (in which case it is impossible to avoid the error of giving one strict interpretation to a melody which is of its nature elastic), or, on the other hand, one may set all the usual time-meaning of modern notation aside, and use symbols which have no strict time-significance, but which, fixing only the sequence and pitch of the notes, will allow the singers freedom of rhythm. This last is the course which I have adopted, and the justification of the method can only be this, that it makes it easy to sing the music properly. Before attempting the four-part singing of any of these tunes, the melody must be known to the singers, and its rhythm understood or agreed upon. This is always advisable, though the simplest tunes in this book (and this No. 29 is one) fall naturally into modern bars, and might be read off fluently enough; but in these simplest melodies it is important not to allow the feeling of bars to equalise the value of the notes, and so cut up the melody into unyielding blocks. After these remarks, the notation adopted will be readily understood with the following explanation:
The notes (semibreve, minim, and crotchet) have not their proper relative values. As a rule the notes in ligature are of less time-value than the notes which are not in ligature.
When a semibreve, not final, occurs in one of the under parts, this means only that it has two or more notes in ligature passing above it.
The notes in ligature are represented by minims printed closely together.
When an accidental occurs in a ligature, the sharp or flat sign is printed on its proper line or space before the whole ligature, not immediately before the affected note. This is done merely to avoid separating the notes of the ligature.