How could one name the first chord in measure three in Mozart's A-major piano sonata K.331, first movement?

Mozart Sonata in A Major, K. 331, mm. 1-4

It looks like a F#-minor-7th-chord without the fifth, i.e. something like a substitution of the submediant VI for the tonic I.

2 Answers 2


Having thought about this for a while (and being unsatisfied with the lack of detail in my assertion that a D sounds more idiomatic than a C♯), I am posting an answer to elaborate.

My reasons for calling this chord a (modified) IV6 chord include:

  • I've always heard the F♯ to E interval as an unresolved 7-6 suspension.
  • Typical figures for a bass line ascending ^6 ^7 ^1 are 6 6 [5] (or 6 6/5 [5]), yielding IV6 V6 I or IV6 V6/5 I (see the example in Wikipedia's article on the rule of the octave, which harmonizes the ascending major scale as I V4/3 I6 II6/5 V IV6 V6/5 I).
  • The submediant (vi) is typically grouped with the tonic (I), reflecting its function in a deceptive cadence. To prepare the dominant, one typically expects ii and IV. (See the Wikipedia articles on harmonic function and the submediant.)
  • The first variation supports this interpretation; it has a D in the melody at this point.
  • A similar bass line appears in Mozart's variations on Ah, vous dirai-je maman, without the inner pedal, and it is invariably the bass of a IV6 chord.
  • This is great. When I can, I'll post a similar case for C#.
    – Aaron
    Jul 7, 2021 at 14:38
  • @Aaron I'll be curious to see what you come up with. I did find one bit of evidence that I neglected to cherry pick, that some might read as supporting C♯, but I don't think it's structural. The actual harmony in that case is, I believe, ii4/3.
    – phoog
    Jul 7, 2021 at 14:54

It's F# minor without the fifth. The E is a pedal tone.

One way to establish this, is to play the opening measure without the E. The overall sense of harmony is unaffected, which helps demonstrate that the E is independent of the harmonic progression even though it is often a participant in it.

The core harmonic progression is

  • I: First measure
  • V65 (or viio): Second measure
  • vi-V6 (or viio): Third measure

In other words, the progression is defined by the bass motion: 8-7-6-7-8.

  • I would call it a IV6 chord. That is, if I had to add a note there, I would add a D, not a C♯.
    – phoog
    Jul 6, 2021 at 12:55
  • Why do you think that?
    – Anna
    Jul 6, 2021 at 15:47
  • @Anna Are you asking why I think the E is a pedal tone; why I think it's a C# minor chord; both; or something else?
    – Aaron
    Jul 6, 2021 at 16:40
  • Aaron, I was referring to phoog. @phoog So again, why would you call it a IV6 chord?
    – Anna
    Jul 6, 2021 at 22:12
  • 1
    @Anna because a D sounds more idiomatic than a C♯.
    – phoog
    Jul 7, 2021 at 0:23

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service and acknowledge that you have read and understand our privacy policy and code of conduct.

Not the answer you're looking for? Browse other questions tagged or ask your own question.