Byrd’s three pieces were probably composed by the early 1560s. There can have been no liturgical reasons for grouping three settings of the antiphon, and even less for transposing the melody up a fifth, as he does in the second setting. The conclusion is clearly that Byrd was simply writing a triple setting based on the plainsong, but designed to be played together like a sequence of movements, and with a cumulative effect that owes nothing to Catholic or Anglican liturgical considerations. His purpose here is to explore three quite different kinds of counterpoint, a straightforward composer’s problem.
The first setting is in two voices and is in cantus fractus technique. The plainsong is broken up in the left hand at the bass octave, in the lowest part of the instrument, a strikingly original and sonorous effect later also used by Bull and Gibbons that is typical of organ writing. In the second half of this movement, the plainsong can once again be heard in more recognisable form, in the tenor octave of the left hand, but Byrd playfully adds mysterious syncopations and unexpected cross-rhythms to the right-hand counterpoint. A third voice enters near the end, as is usual in such pieces, and announces the texture of the next movement.
The second setting is in three voices, using cantus firmus technique. The plainsong is heard in long notes in the top voice, but it has been transposed up a fifth (making any liturgical link extremely unlikely). The duet heard between the two lower voices starts in rational, imitative manner, but soon breaks down into warring cross-rhythms which end up displacing the beat so that it sounds as if the cantus firmus has gone wrong and slipped out by one beat. This is an aural equivalent to the trompe l’œil effect in painting, where the eye is deceived; here, in a sort of trompe l’oreille, it is the ear that is cheekily misled.
In the third setting the number of voices increases again, to four. This brings the set to its fullest sonority so far, although 6-part chords are heard at the end. It is fully imitative throughout. By comparison with the second setting, here the extra voice is the soprano, added like a sort of descant over the plainsong (which is in the alto), much as Byrd usually adds a descant in the last section of his song variations. In the first cell of imitation each of the three non-plainsong voices (soprano, tenor, bass) gets three different statements of the countersubject, in crotchets moving by small intervallic jumps (Morley’s ‘disjunct deduction’). But each statement is different melodically, such is the nature of Byrd’s flexible counterpoint since he likes pulling about the intervals and note values, stretching and compressing them to give a new emphasis to the melodic and rhythmic cell. The second cell enters with a new idea in flowing quavers, in conjunct stepwise motion (Morley’s ‘continuall deduction’), and introduces some expressive false relations which, by being placed on many different degrees of the scale, add an altogether unusual harmonic variety. The third cell presents a new musical idea in crotchets that steadily march upwards; the music becomes more chordal as it reaches the highest notes of the keyboard. The long final cell of imitation (a theme that rises four notes in crotchets before falling in quavers) grows effortlessly out of the third cell. Almost unawares, the plainsong has disappeared from sight as the alto became increasingly ornamented and started joining in the general imitative discourse. After reaching again to the top of the instrument, Byrd’s magnificent closing paragraph allows this profound and sonorous piece to sink calmly back to the lowest registers, where the first setting of Clarifica me had started, a most satisfying effect that owes as much to the nature of the instrument and to the resonances in a large building as it does to musical ideas noted on paper. Neighbour places this movement ‘beside the best of Redford and Tallis among the finest things in English organ music’.
from notes by Davitt Moroney © 1999