B minor scale, interval, and chord labelling
An HSC candidate submits a 12-bar composition exercise in B minor. The key signature has two sharps. In bars 1–4 the melody ascends B–C♯–D–E–F♯–G–A♯–B; the candidate labels this 'B melodic minor ascending.' In bar 6 the interval E up to A♯ is labelled 'perfect fourth.' In bar 9 the chord B–D–F♯–A is labelled 'B minor seventh,' although the preceding bar uses A♯ as the leading tone. The candidate's teacher notes that the written scale contains an augmented second between G and A♯, and that the chord label ignores the harmonic-minor context. The candidate can play the scale accurately but cannot explain why the sixth degree changes. The exercise is due in three days and the candidate wants to avoid losing marks for notation, interval naming, and chord labelling.
1. Correct the scale label and the interval label, explaining the scale-degree reasoning in each case.
Read the worked answer
B natural minor is B–C♯–D–E–F♯–G–A. The harmonic minor raises the seventh degree to A♯, giving B–C♯–D–E–F♯–G–A♯. The melodic minor ascending raises both the sixth and seventh, giving B–C♯–D–E–F♯–G♯–A♯. The candidate's scale has G natural with A♯, so it is harmonic minor, not melodic minor ascending. That distinction matters because the raised sixth in melodic minor smooths the step from G♯ to A♯. The interval from E up to A♯ is not a perfect fourth: E–A is a perfect fourth of five semitones, and raising A to A♯ adds a semitone, producing an augmented fourth of six semitones. It is enharmonically a diminished fifth but must be spelled as an augmented fourth in this context. Correct labels: 'B harmonic minor' and 'augmented fourth.'
2. The chord in bar 9 is B–D–F♯–A. Explain whether 'B minor seventh' is correct in context, and give the chord's function in B minor if A is A♯ instead.
Read the worked answer
Spelled B–D–F♯–A, the chord is a B minor seventh: minor third D, perfect fifth F♯, minor seventh A. That label is correct only if A natural is intended. In B harmonic minor the diatonic seventh on the tonic uses A♯: B–D–F♯–A♯, a minor-major seventh (Bm(maj7)), not Bm7. In the progression i–iv–V7–i, the dominant is F♯7 = F♯–A♯–C♯–E; the leading tone A♯ must resolve up to B. If the student doubled A♯ in the V7 chord, the doubled leading tone creates a forced resolution and likely parallel octaves. The fix is to double the fifth or root in the dominant, not the leading tone, and to resolve A♯ to B and E to D (or F♯).
3. A classmate says the augmented second is always an error. Evaluate this claim with reference to harmonic minor and typical melodic practice.
Read the worked answer
The claim is too strong. The augmented second between G and A♯ is built into harmonic minor because raising the seventh degree is necessary for a strong dominant. In instrumental writing the leap can be effective, but in vocal lines and four-part exercises it is usually avoided because it is hard to tune and sounds like a chromatic distortion of the scale. Melodic minor solves the problem by raising G to G♯ ascending, turning the augmented second into a whole step; descending, it reverts to natural minor. A composer may still use the harmonic-minor leap for colour, but a theory marker would treat it as a stylistic choice, not automatically an error. The real error in the candidate's work is the wrong label, not the presence of the interval.