The interval and distance of imitation between voices may be freely
varied. The most likely intervals are upper and lower fifth, fourth, and
octave; however, any other diatonic interval (including seconds or
sevenths) may appear.
The distance of imitation may be used dynamically to create pairs of
imitating voices, compress the entrances for dramatic effect, or create an
imitative texture against a sole free voice. The distance may also be
adjusted to create closure at important structural cadences.
Augmentation or diminution of a duration in a point of imitation is
another method of controlling the distance between successive entrances
or generate an overlap between imitative phrases. Whole short passages
may have altered rhythmic values, as well as a single note.
The adjustment of melodic intervals in a point of imitation may be
used to preserve the modal integrity or to change the interval of imitation.
A repetition of a point of imitation after the voices have entered adds
cohesion (like the baroque "false entrance").
Sometimes, only the rhythm of the incipit is replicated with a
complemetary (like inverted) or totally different melodic contour.
2. The voices themselves:
Attention must be paid to the global arrangement of successive
entrances. E.g. An SATB entrance may be followed in a successive
phrase by BATS or a kind of rotation with ATBS, TBSA, etc. Composers
often build in global symmetry with this kind of scheme.
The first duration in a point of imitation my be truncated or lenghtened
to create continuity or highlight an association of voices. In a Plainchant,
the first pitch may be a repeated note from the beginning of the chant.
The tessitura of the entrance has an effect on the dramatic shape of
the phrase: if all entrances are at the respective top of vocal ranges, more
tenson will result. A progressive increase or decrease in tessitura would
create a corresponding contour in drama.
The use of the text is an art in itself: melismatic setting of parts of the
text often mirrors a similar melisma in a chant with the same words.
Melisma may be associated with high contrapuntal passages, as opposed
to a syllabic setting which may occur in homophony.
3. Special Techniques:
Imitation by inversion may be used in the middle of a piece.
Invertible counterpoint at octave, tenth, or twelfth may be used
between two or more voices to extend a phrase. This technique may be
used in conjunction with transposition or with interleaved vertical placement
of voices.
Voice crossing often resolves spatial difficulties; however, the voices
always resume normal position by the end of the phrase.
Suspension dissonance has important uses at cadences, and to
smooth over entrances of imitating vices.
Cambiata, echapee, double neighbor, double passing tone, dissonant
preparation (where the final upbeat anticipates the strong-beat dissonace)
are the kind of nonessential dissonances which control inflection.
Long note values tend to prevail atthe beginings of phrases or the
whole piece, while shorter note values (and corresponding greater pitch
density) are typical of later sections.
End-stop cadences denote larger divisions of a piece, while
continuing cadences link successive phrases.
Voice ranges often conform to species of tetrachord and pentachord
in the modal matrix.
Phrases seem to be comparatively short: often performed in one
breath, thus implying certain tempo indications.
Pitch is relative within approximately a minor third. White notes plus
Bb, Eb, F#, and C# are the usual array.
There are really only 8 modes: D, E, F, G, with their hypo (plagal)
pairs. D and F modes cadence on 1,3,5 while E and G modes cadence on
1,4,5.
The last cadence must be on the Final of the predominant mode of
the piece. In extended sectional pieces, like Passion settings, there may be
a single mode used throughout or perhaps two modes.
P.R.