Rules
No mark without its rule: the full list of the checker's rules, with their severity and the chapter and page of Piston each one comes from.
- Parallel fifths: Two voices a perfect fifth apart do not move to another perfect fifth in the next chord, whether by similar or contrary motion, nor as compound intervals (twelfth). Between soprano and bass, a diminished fifth does not move to a perfect fifth either. A perfect fifth may move to a diminished one. (Piston, ch. 3, pp. 29–30 and 34)
- Parallel octaves: Two voices an octave or a unison apart do not move to another octave or unison in the next chord, whether by similar or contrary motion, nor as compound intervals (fifteenth): the two voices would lose their independence. (Piston, ch. 3, pp. 29–30 and 34)
- Spacing between voices: Adjacent upper voices (soprano–alto and alto–tenor) are no more than a perfect octave apart. There is no limit between tenor and bass. (Piston, ch. 2, p. 16)
- Doubled leading tone: The leading tone is never doubled: in no chord or inversion does it appear in two voices. (Piston, ch. 2, p. 16; ch. 3, p. 27)
- Doubled leading tone in III: The exception to the previous rule: when the leading tone is the fifth of III, it may be doubled. It is allowed, but flagged so you know it is an exception. (Piston, ch. 2, p. 16; ch. 3, p. 27)
- Unresolved leading tone: The leading tone (the note a semitone below the tonic) rises by semitone to the tonic when the next chord contains it, in any voice. If the next chord does not contain the tonic, it is not required. (Piston, ch. 3, pp. 32–33 and 35)
- Direct octaves: Soprano and bass do not reach a perfect octave by similar motion (both in the same direction) with a leap in the soprano. It is fine if the soprano moves by step, or if the octave is reached by contrary motion. (Piston, ch. 3, pp. 30–32 and 35)
- Direct fifths: Like direct octaves: soprano and bass do not reach a perfect fifth by similar motion with a leap in the soprano. It is fine if the soprano moves by step, or by contrary motion. (Piston, ch. 3, pp. 30–32 and 35)
- Direct fifths or octaves by leap in both voices: No pair of voices reaches a perfect fifth or octave with both voices leaping in the same direction. It is allowed when the same chord only changes position and, in V → I, with the leading tone falling to the fifth in an inner voice. (Piston, ch. 3, pp. 30–31 and 34)
- Out of range: Each voice sings within its range: soprano C4 to G5, alto G3 to D5, tenor C3 to G4 and bass E2 to C4. Going outside it now and then is not serious, so it is a warning. (Piston, ch. 2, p. 15)
- Large leap: From one chord to the next, soprano, alto and tenor do not leap more than a perfect octave. In the bass, leaps of a sixth or more are flagged as a warning. (Piston, ch. 3, pp. 24 and 28)
- Voice crossing: In each chord, every voice stays below the one above it: the alto does not go below the tenor, nor the tenor below the bass, nor the soprano below the alto. Crossing between alto and tenor is only a warning. (Piston, ch. 3, p. 34)
- Voice overlap: From one chord to the next, a voice does not rise above the note the voice above has just left, nor fall below the note the voice below has left (landing exactly on that note also counts). The leading tone rising to the tonic together with the bass in V → I is allowed. (Piston, ch. 3, p. 33)
- Ending away from the tonic: At the end of the exercise, a final cadence: the tonic chord in root position (in minor, also with a Picardy third). With the tonic inverted, the conclusive cadence has not yet arrived. Otherwise, it is flagged as a warning. Starting away from the tonic, on the other hand, is fine. (Piston, ch. 13, p. 200; ch. 11, pp. 165–167)
- Doubled bass in first inversion: In first inversion, the bass is not doubled when it is not a tonal degree (III, VI or VII). If the bass is a tonal degree (I, II, IV or V), doubling it is correct. (Piston, ch. 6, p. 69)
- Unusual progression: Flags a chord connection that is not among Piston's usual ones (and I → II with II in root position). It is not an error: it is a pointer. (Piston, ch. 3, pp. 21–22; ch. 4, p. 45)
- Incomplete inversion: An inverted chord is complete: with its root, third and fifth. (Piston, ch. 6, p. 69)
- Chord without a third: A chord never goes without its third: without it, it sounds like a bare fifth. The fifth may be omitted (for example, in V7 or in the I that follows it). (Piston, ch. 3, p. 27; ch. 15, p. 239)
- The chord does not match the figures: If the exercise gives the figures, the chord written is the one on that degree, in the inversion and with or without the seventh that the figures say. In minor, every form of the degree is valid. (Piston, ch. 4, pp. 42–45; ch. 6, pp. 68–69)
- Cross relation: If a note appears altered in the next chord (F and F♯), the chromatic change happens within one voice, not split between two. In minor it is allowed on the sixth and seventh degrees (those of the melodic minor scale). (Piston, ch. 16, pp. 252–253)
- Unresolved seventh: The seventh of a seventh chord falls by step in the next chord. Exceptions: the same chord in another position; in V7 → I⁶ the seventh may rise if the bass takes its resolution; a major seventh may rise to the root; and in V7 → IV it is held as the root of IV. (Piston, ch. 15, pp. 238–243; ch. 17, p. 266; ch. 23, p. 344)
- Doubled root after VII7: When the leading-tone seventh goes to I, the tonic chord does not double its root: the second degree rises to the third to avoid parallel fifths. (Piston, ch. 22, p. 335)
- VII⁶₅ does not go to I⁶: With the second degree in the bass (VII⁶₅), the leading-tone and diminished sevenths resolve to I in first inversion (I⁶). (Piston, ch. 21, p. 321; ch. 22, p. 336)
- Second degree of the diminished seventh: In a diminished seventh going to I, the second degree rises to the third. It may fall to the tonic if it lies above the lowered sixth degree; if it lies below, it is flagged as less usual. (Piston, ch. 21, p. 320)
- Unprepared seventh: The seventh of non-dominant chords (II7, IV7…) is prepared: the same note, in the same voice, in the previous chord. The seventh of V7 does not need it. (Piston, ch. 23, p. 342)
- Misused six-four chord: The six-four chord is only used in three ways: cadential (I⁶₄ on a strong beat going to V over the same bass), auxiliary (the bass stays and the chords before and after are the same) or passing (the bass arrives and continues by step in the same direction). (Piston, ch. 10, pp. 151–158)
- Unexplained non-chord tone: A note of the given voice that is not in the chord must be a recognizable non-chord tone: passing tone, neighbor tone, échappée, anticipation, appoggiatura, suspension, incomplete neighbor or near tone. If not, it has to be harmonized. (Piston, ch. 8, pp. 110–123)
- Doubled secondary leading tone: The leading tone of a secondary dominant (for example, the F♯ of V/V in C major) is not doubled: for a moment it is a leading tone. (Piston, ch. 16, p. 251)
- Unresolved secondary leading tone: In a secondary dominant (V/V, V7/IV…), its leading tone rises by semitone to its tonic, just like the leading tone of the key. It may fall chromatically in the same voice (V7/V → V7). (Piston, ch. 16, pp. 251 and 253)
- Augmented or diminished interval: Augmented and diminished melodic intervals (augmented second, tritone, diminished seventh…) are best avoided. It is not serious, especially in an inner voice, so it is a warning. A chromatic semitone in one voice (F → F♯) does not count. (Piston, ch. 3, p. 28; ch. 4, p. 46)
- All four voices in the same direction: Between two root-position triads, the four voices do not all move up or all move down. In the final cadence it is allowed if at least one voice moves by step. (Piston, ch. 3, pp. 34–35)
- Minor V before I: In minor, the V that goes to I is always major, with the leading tone (G♯ in A minor). The minor V, with the natural seventh degree, is used in a line descending toward IV or VI, never before I. (Piston, ch. 4, pp. 40 and 45)
- Minor-mode VI and VII by direction: In minor, the sixth and seventh degrees follow the melodic minor scale: raised when rising toward the tonic, natural when falling. So the raised sixth rises to the leading tone and the natural seventh does not rise to the tonic of I. (Piston, ch. 4, pp. 41–44)
- Second moving to a unison: Two voices a second apart do not move to a unison: Piston only allows it from a minor second, when the upper voice is an anticipation. (Piston, ch. 15, p. 237)
- Ninth moving to an octave: Two voices a ninth apart move to an octave only if the upper voice is the one that moves (the ninth resolving downwards, as in the 9–8 suspension). If the lower voice rises or falls, it is marked. (Piston, ch. 15, p. 237)