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    Enharmonic Modulation via dim7

    Dear Colleagues,

    If some of you are interested in modulation in general, please take a look at the short youtube video "MT III Enharmonic Modulation via dim7" (typing this title or using the link below).

    Two days ago we devised one "quazi enharmonic modulation" in my theory III class which used the same B dim7 chord to modulate from C major to A-flat major. The interesting thing is that we did not need to respell the chord, and this is why I named the process "quazi enharmonic". A leading tone dominant turns into an altered subdominant chord (SII7 alt. or common tone dim.7) and resolves into T6 of the new key. An interesting effect. The class managed to sing this fairly well with one trial before the recording.


    Thank you,


    Best regards,




    Dr. Dimitar Ninov

    Texas State University



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    • 5 Comments sorted by Votes Date Added
    • Thank you for this example Dr. Ninov.  Is there not a generalized rule that any tone (or edge) of a symmetrical chord - diminised, diminished 7th, or augmented can function as leading tone with many resolutions to major/minor/deceptive destinations?  In other words a Bdim7 can resolve to:

      C, Cm, Am/C, Ab/C

      Eb(D#), Ebm(D#m), B/D#, G#m/D#

      F#, F#m, D#m/F#, D/F#

      A, Am, F#m/A, F/A

      And the Augmented chord functions the same way . . . 

      Tchaikovsky has an excellent chapter on modulation through diminished chords in his harmony text available for free download on imslp.org

      Thank you for the video and modulation lesson.

    • Dear Carson,

      Thanks for your message. Yes, a single dim7 chord may function in 24 keys as either a dominant or an altered subdominant (which is also a doiminant of the dominant), or a secondary dominant. In all of these cases the resolution is not deceptive if it finds its targeted tonic (or local tonic). If not, a number of deceptieve resolutions is always open. In my example, the resolution of Bdim7 into Ab major is not deceptive; the chord resolves there as an altered SII7 (II7 with a raised root and third). THe nickname for this chord in most American books is "common tone diminished seventh", poinitng out that this chord may resolve into a triad whose leading tone it does not contain; it contains its root.

      Best regards,


    • So one might say there are "primary" levels and "secondary" levels of resolution with vast resolution possibilities based on degrees: dominant relationships, subdominant relationships, other secondary dominants, etc.  I wonder if it is helpful to identify levels for primary and secondary resolutions?  

    • Perhaps it is more appropriate to speak of stronger expectations based on more frequent cases of resolutions such as dim7 as a dominant or secondary dominant. But I like your attempt to clarify situations, and you can choose a terminology which appeals to you. By the way, the typical chords with an augmented sixth function as a diminished seventh chord (D or S, main or secondary), depending on the resolution - but are not so universal, although several interesting resolutions are possible that are not studied in the conventional course.

      Thanks for your interest. Have you seen my other video which is much more complex in temrs of modulatory means? Modulatory excursion (on youtube)

    • Yes Dimitar I did see your other video and enjoyed it very much.  Have you explored the possibility of putting your videos on SMT-V? I just recently began paying attention to that section of SMT content.  I particularly liked the video on Haydn's use of counterpoint.  

      Regarding modulation I tend to view it mathematically as making choices and destination decisions based on regions with similar or disimilar subsets.  Modulation as a general principle facilitates harmonic contrast and alleviates monotony.