I'm composing a traditional four-part part-writing piece with a soprano, alto, tenor and bass. The song progresses from a F Major chord to an A Major chord. In the former chord, the bass is on C, and in the latter, I want to move the bass up to C#.

My question is, would such a move be allowable (assuming no issues arose with the other voices)? I know certain movements aren't allowed, but couldn't find any information on the augmented unison interval in particular.

  • 2
    If it sounds good, why does it matter if it's "allowed"? Commented Aug 30, 2015 at 5:20

2 Answers 2


Yes, moving chromatically within one voice is totally fine. It's actually a secret trick composers use to get choirs to sing atonal / pantonal music. That said, if it's too chromatic, you'll have problems.

Typically in choral writing, certain movements are "not allowed" because they are difficult to "hear" in the mind before the person sings. Intervals such as tritones and augmented-seconds are both odd for this reason.

  • 1
    'Not allowed' is perhaps a little harsh. Lenny got away with a tritone in 'Maria'!
    – Tim
    Commented Aug 30, 2015 at 7:06
  • @Tim Yes, I meant to put those two words in quotes (now edited) but forgot. Lenny and thousands of other composers broke the "rules" to achieve great music. It's less about hard rules and more about being considerate to performers. Regarding Lenny, it was how he used the tritone that allowed him to be successful with that piece. Commented Aug 30, 2015 at 16:40

The half step motion is allowed, but you may have difficulty with voice leading. If your voices (from bass to soprano) are C/F/A/f and you go directly to A major with C#/E/A/e, the tenor and soprano move in parallel octaves, which violates the four-part voice leading rules. Same if C/A/c/f goes to C#/A/c#/e; the bass and alto move in parallel octaves. Possible solutions are C/A/c/f to C#/A/A/e, or C/F/A/f to C#/A/A/e.

If your goal is to progress to an A major chord but not necessarily to the key of A major, then C/F/A/f to C#/G/A/e (an A major 7th chord) would be acceptable; but that would be leading you toward the key of D (major or minor).

  • 2nd inversion F to 1st inversion A7 would work quite well - one of the F's moves to G. Substitutes the dominant of the relative minor for the dominant that would be expected after a tonic 2nd inversion - in the right circumstances, could make an effective modulation.
    – user16935
    Commented Aug 30, 2015 at 15:00
  • What about C/F/A/c to C#/E/A/A?
    – Divide1918
    Commented May 8, 2022 at 14:42

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