Chorale Harmonization: Doubling a Leading Tone in a Deceptive Cadence

In G major, the notes written are G (bass), D (tenor), B (alto), A (soprano). The chord tones present are G–B–D, which spell G major (I), not vi. The A in the soprano is a non-chord tone (a 2–3 or appoggiatura figure), not a chord member. So the student has not written vi at all; they have written a tonic chord with a dissonant soprano. The instructor's objection is twofold: (1) the chord is mislabeled - it is I, not vi; (2) a deceptive cadence requires V moving to vi (or V–VI in minor contexts), meaning the bass must move by step from the dominant root to the submediant root. Here the bass sits on G, the tonic, so there is no dominant-to-submediant bass motion. The "doubled third" comment likely refers to the fact that in a true vi chord (E–G–B), doubling the third (G) is the least desirable doubling; the student's voicing happens to contain two Gs (bass and, if we count the chord, the third), which is the doubling the instructor flagged. The fix: change the bass to E and re-voice the chord as E–G–B with the A in the soprano handled as a passing or neighbor tone, or respell the soprano's A as a chord tone of vi only if the chord is actually vi (A is not in vi, so the A must be treated as non-chord).

A genuine deceptive cadence in G major is V–vi: D major (D–F♯–A) resolving to E minor (E–G–B). The soprano A is a chord tone of V (the fifth), so it can be kept on the dominant chord, but on the resolution the soprano must move to a chord tone of vi - either G (third) or B (fifth) or E (root). If the melody must land on A at the cadence point, then A is a non-chord tone over vi and should be approached and left as a suspension or appoggiatura, not treated as a chord member.

A clean revision: bass D → E (step up, the defining motion of a deceptive cadence); tenor F♯ → G; alto A → B; soprano A → G (or hold A as a 4–3 suspension over vi, resolving to G). Rules to cite:

• The leading tone (F♯) in an outer voice must resolve up to the tonic (G); in an inner voice it may fall to the fifth, but resolving up is safer.
• The bass moves by step, which is what distinguishes a deceptive cadence from a plagal or authentic one.
• Doubling in vi: double the third (G) or the root (E); avoid doubling the leading tone or the fifth when it creates parallel issues.
• Check for parallel fifths/octaves between bass and any upper voice; D–E in the bass against A–B in the alto would create parallel fifths if the alto moves A→B while bass moves D→E? No - D–A is a fifth and E–B is a fifth, so that pairing is parallel fifths and must be avoided by moving the alto differently (e.g., A→G). This is the kind of detail the instructor is testing.

Belonging to a pitch collection is not the same as functioning as a chord. E minor contains E–F♯–G–A–B–C–D. The student's notes G, D, B, A are all members of that collection, but chord identity is determined by the root and the interval structure above it, not by set membership. The sounding result is a G-major triad (G–B–D) with an A added; the A is a non-chord tone because it is a second above the bass and does not fit the tertian stack G–B–D. Calling it "vi" because the notes are diatonic to E minor conflates key context with chord function: in G major, vi is E–G–B, and the bass must be E for the chord to be vi in root position. A chord with G in the bass and B, D above is I (or, if A is included as a chord tone, it would be a Gadd9 or a I with an added second - not vi). The instructor's point is that the student has misidentified the root and therefore the Roman numeral; the fix is to identify the root from the bass and the stacked thirds, then assign the numeral relative to the established key of G major.