I was recently approached by a student, who swore that they had read that exposed (i.e. outer voice hidden) 8ves/5ths were permitted between different inversions of the same chord. He said he came across this instruction in our subject textbook (Laitz: The complete musician) but, when pressed, couldn't deliver. I got curious, and quickly found a few informal (i.e. online) resources that corroborated this, but nothing that I would trust as authoritative.

I then did a quick survey of the texts I have at hand. The majority of these only have the one, obvious exception: that exposed 8ves/5ths are only allowed if the soprano moves by step. For Laitz, along with Clendinning/Marvin (The Musician's Guide...) and Kostka (Tonal Harmony), this is the only allowable exception. Aldwell/Schachter (Harmony and Voice Leading) has a really perfect, excellent extended passage (p.109 of 4ed, FYI) on the numerous factors that influence the degree to which hiddens might stand out, and when they might be okay, and generally advises the reader to trust their ears, before eventually 'summarising' all that good, thorough, musical advice, to simply 'avoid them unless the upper voice moves by step'. Schoenberg's take on all this, and on the 'phantoms of orthodoxy', is obviously hilarious.

I also looked at Bach, at the 6 instances of exposed perfect consonances that occur in the chorales (as charted by Luke Dahn). Of these, 3 are within different voicings of the same chord, and 3 are across chord changes. So... No obvious guiding principle, and I'd guess he was just trusting his ears.

But... as I was looking over the texts, there were a few curious, additional rules I noted as I was going.

  • In Burstein/Strauss (Concise introduction to Tonal Harmony), they note that perfect consonances between any combination of voices should never be approached by similar motion if coming from a dissonance (e.g. An 8ve b/w tenor and soprano cannot be approached from a 7th or a 9th).
  • The AMEB (Australian Music Examinations Board) Grade 4 Theory Workbook says that exposed 5ths are allowed if the soprano approaches the 5th from the 3rd of the previous chord.

Both of these I had never heard before, and am curious to know (i.e. would be surprised to find out) if they were supported elsewhere.

So... after all that, my questions are:

  • Does anyone know of any authoritative source that corroborates the idea that exposed 5ths/8ves are allowed within two different voicings of the same chord?
  • Excluding the obvious soprano-moving-by-step and using-at-least-one-inner-voice, does anyone know of any other curious exceptions as to when hiddens are allowed/disallowed?
  • Can you link to the Bach examples, or any of them? I'm curious.
    – phoog
    Sep 12, 2023 at 20:32
  • 1
    The resource for Bach doing anything unusual is: lukedahn.net/ChoraleIndex.htm - it's a great resource! The exposed are founds in part V, point g. You can then cross-reference with scores at bach-chorales.com/Index.htm
    – mb_altho
    Sep 12, 2023 at 23:40


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