The Tritone Leap and the Hidden Fifth
A candidate submits a first-species counterpoint exercise in D Dorian. The cantus firmus (given) is: D4–F4–E4–D4–G4–F4–A4–G4–F4–D4. The candidate's counterpoint is: F4–A4–G4–F4–D5–C5–F5–B4–A4–F4. The exercise is marked in whole notes, with no accidentals. The examiner must assess two flagged issues: (1) the leap from F5 down to B4 between the seventh and eighth notes, and (2) the approach to the fifth between the fourth and fifth notes, where the dyad D4–F4 (a third) moves to G4–D5 (a fifth) with both voices moving upward and the upper voice leaping a sixth. The candidate argues that the tritone leap is acceptable because it is a diminished fifth (not an augmented fourth), and that the direct fifth is acceptable because the upper voice leaps by a consonant interval. The examiner must decide whether either argument has merit, and propose corrections that preserve the line's overall shape.
1. Identify the two errors and explain why each is a fault in strict first-species counterpoint. Address the candidate's arguments directly.
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Error 1 is the leap from F5 down to B4, a diminished fifth. In first species, any tritone leap is forbidden: it destabilizes the modal centre and is difficult to sing accurately. The candidate's distinction between a diminished fifth and an augmented fourth is irrelevant; both are tritones and both are prohibited as leaps. Error 2 is the direct (hidden) fifth between the fourth and fifth notes. The dyad D4–F4 (a third) moves to G4–D5 (a fifth), with both voices moving upward and the upper voice leaping a sixth into the perfect fifth. In strict first species, direct fifths are allowed only when the upper voice moves by step; a leap into the fifth is a fault. The candidate's claim that a consonant leap is acceptable confuses leap quality with the voice-leading rule. Both errors are therefore valid.
2. Propose two corrections: one that fixes the tritone leap while preserving the general contour, and one that fixes the direct fifth. Show the corrected notes and explain the voice-leading reasoning.
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To fix the tritone leap, change the seventh note from F5 to E5 or C5 so that the motion into B4 is a consonant interval. For example, C5–B4 is a step and preserves the descending shape; the resulting dyads A4–C5 (third) and G4–B4 (third) are consonant. To fix the direct fifth, change the approach so that the upper voice moves by step into the fifth, or avoid the leap into the fifth. One solution is to change the fifth note from D5 to B4: the dyad becomes G4–B4 (a third), and the motion from F4 to B4 would need checking, because F4–B4 is a tritone. A safer correction is to change the fourth note from F4 to A4 and the fifth note from D5 to B4: the dyads become D4–A4 (fifth) then G4–B4 (third), eliminating the direct fifth. The candidate must then recheck the surrounding intervals for parallel perfect intervals.
3. Would the direct fifth be acceptable if the upper voice moved by step instead of leap? Justify with reference to species counterpoint rules.
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Yes. In strict first species, a direct fifth is tolerated when the upper voice moves by step into the perfect fifth, because the stepwise motion softens the arrival and preserves the independence of the voices. The rule is designed to prevent the upper voice from leaping into a perfect interval, which would emphasize the hollow sonority and weaken the counterpoint. If the upper voice moved by step, the same harmonic arrival would be acceptable, provided the preceding interval is not already a fifth (which would create parallel fifths). The candidate should therefore distinguish between direct fifths approached by leap (fault) and those approached by step (acceptable). This is why the correction should focus on the upper voice's motion, not merely on the interval quality.