Mode IV Discrepancy -
  • M. Jackson Osborn
    Posts: 8,391
    A friend called me the other night asking an answer to why a mode iv communion did not end on the final of the mode. I could not answer his question, so I come to the forum for some explanatory offerings.

    At question is the communion Tollite hostias, whose c-clef centres on the third line from the bottom, and whose final note, being B, is not the final of the mode.

    We searched and found that other propers (introits, offertories, alleluias) share this condition, though by far most have their clefs on the top line and have the correct final, E.

    What is the reason for this discrepancy?
    I have noticed this before but never pursued it.
  • Charles_Weaver
    Posts: 64
    The modes, most especially the even-numbered modes, have alternate finals a fifth above the normal final. This is something you see a lot in graduals like Haec dies, which ends on A but is in mode 2. You also see it in the simple Salve Regina, which ends on C but is in mode 5. Another commonly encountered example with mode 4 ending on B is the Gloria, Sanctus, and Agnus of Mass I.

    Usually these moments have to do with unusual placement of B-natural and B-flat. The communion Beatus servus is the classic example, which seems to be sometimes in mode two and sometimes in mode 4, but is written with a final on A so that both of the possibilities (whole step above the final and half step above the final) are possible. In Tollite hostias, the descent to F on "Adorate Dominum" would have to go to B-flat if it were notated with a final of E, but that note doesn't really exist in the medieval scale. If you look at the Guidonian hand, the B in that octave (the base of the thumb, and the B a ninth below middle C) can only be B mi or B natural as we now call it. Writing the chant with a final of B takes away that issue, while preserving all the appropriate intervals in the melody.
    Thanked by 2M. Jackson Osborn tomjaw
  • MatthewRoth
    Posts: 2,208
    We have started doing verses, and this plus Per Signum of September 14, draws out these aspects particularly Tollite, because it feels a little odd to return to the normal psalm verse, but our schola didn’t have a problem singing the first three notes with the correct, non-transposed clef… and this is another reason why not only is the Guidonian hand useful, it’s easy to use in this mode. In this case, Do really is Fa in an interesting and obvious way. It’s not just a fiction made complicated by a preference in our editions for Do clefs.

    I have wondered for a minute now why some chants are not so rendered but the answer may be because the musica ficta required of the low B-flat is perhaps easier in the end.
    Thanked by 2M. Jackson Osborn tomjaw
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