Before a new note is written, clefs, range, and cadences reveal the tonal world in which every melodic choice must live.

The borrowed bass comes from a Palestrina setting written in chiavette, the high-clef arrangement used for particular modal and vocal dispositions. Joined to the final on G, those clefs identify the seventh tonus, not the eighth. The distinction is practical, not antiquarian: clefs coordinate register, range, cadential degrees, and the characteristic behavior expected from each voice.

Among the parts, the tenor is the principal guide to modal disposition. In the seventh tonus it projects the relevant fourth species of diapente and first species of diatessaron, so its written register must remain comparatively high. Performance may transpose chiavette downward, but composition begins inside the notated system, where the clefs disclose which melodic paths are stylistically available.

A Renaissance line is not merely a chain of acceptable vertical intervals. Its phrases acquire direction from cadential hierarchy: some cadences articulate firm arrivals, others are delayed, evaded, or lightly suggested. The bass already contains evidence of these destinations. Reading its long notes, rests, and characteristic degrees allows the new voice to join an existing modal argument rather than decorate a harmonic foundation.

The borrowed line supplies the subjects, but convincing counterpoint depends on knowing when to imitate, alter, anticipate, or stop them.

The bass opens with an ascending diatessaron, a figure that embodies the tonus and naturally invites imitation in the tenor. A literal answer soon produces an exposed fourth resembling an appoggiatura, so the continuation must change. Redirecting the melody through a fifth toward a third preserves the subject's identity while restoring stylistic control—a useful reminder that imitation is a method, not a mechanical command.

When the bass holds a long note before presenting its next figure, the tenor can anticipate the imitation instead of waiting. Working backward from a suitable consonance reveals a plausible entry two tactus earlier. If the result then lingers too long on one sonority, the subject's opening may be trimmed. This cutting of the head keeps the texture mobile while a dotted rhythm gives the preceding phrase a graceful close.

A convincing clausula needs proper preparation, suspension, and resolution, often heard as a 7–6 motion before the octave. Yet every possible cadence should not become a full stop. A gesture toward G may be evaded, and an apparent arrival on C may remain local. Such cadential restraint preserves hierarchy: listeners sense several doors, but the counterpoint chooses carefully which ones to open.

Transformation, rhythmic discipline, and selective adaptation turn inherited material into a coherent duo rather than a reduced four-part score.

Static passages invite transformation rather than invention. A previous idea can return in melodic inversion, with contrary motion preserving its inner organization and the modal placement of semitones. This is not a geometric flip performed blindly: solmization still governs the line. Recalling familiar material after a cadence creates coherence, while syncopation and dotted notes keep the return from sounding merely recycled.

In runs of quicker black notes, the governing pattern is consonance–dissonance–consonance–dissonance. Structurally weighted notes remain consonant; intervening notes may pass through friction. Even a unison on an upbeat or an occasional dissonant minim can work when imitation and rhythm justify it. The lesson is not laxity but contextual judgment: duration, accent, approach, and resolution determine an interval's character.

A sustained D can support a moving figure as 5–6–8–6, then exchange roles through invertible counterpoint at the tenth: fifths become sixths, sixths become fifths, and octaves become thirds. Because the source was written for four voices, a long empty span may be shortened for a duo. Such selective adaptation honors the model more faithfully than literal copying, guiding the new tenor toward a lucid final unison.