Here’s an excerpt from Beethoven’s piano sonata no. 5, second movement, measures 13-16, with my analysis in blue (key of Ab major, 2/4 time):

Beethoven Op. 10, No. 1, "Adagio Molto", mm. 13–16, with analysis

My question is about the notes and chords in the blue box. At first I thought it was a Neapolitan or augmented sixth chord, but it’s not. I’m very curious about the augmented first degrees (A naturals) on relatively strong beats. Is this just chromatic material or is there something functional happening here?

2 Answers 2


The overall harmonic motion of the measure is from IV to ii6. The transition is made through the augmented triad rooted on 4 — in essence, the first A-natural is just an accented chromatic passing tone.1

IV moving to ii6 via IV+

However, the arrival on the ii chord is intensified by the presence of viio/ii (over the Db pedal tone), also in a relatively accented position.

Measure 14 harmonic analysis

1 This same chromatic motion between a major chord and its relative minor in first inversion forms the classic accompaniment of the song "Brazil" ("Aquarela do Brasil", Ary Barroso [1939]). I really like this progression and also mention it in How do I use augmented chords in my progressions?.

  • Would that make the A naturals part of a iimaj7 (minor-major) chord? Commented Nov 15, 2021 at 3:30
  • @ToddWilcox Would appreciate your feedback on whether my edit better explains.
    – Aaron
    Commented Nov 15, 2021 at 4:38
  • 1
    In other words, "Is this just chromatic material or is there something functional happening here," Yes and yes. Commented Nov 15, 2021 at 13:24
  • 1
    @ToddWilcox That's very interesting about the delayed Db/F. Not only the delay, but being a dyad, it's inherently ambiguous, plus the Ab, being at the weakest part of the beat, is barely heard as part of the chord.
    – Aaron
    Commented Nov 15, 2021 at 15:20
  • 1
    @ToddWilcox No worries. The kid in me is looking forward to my new hat.
    – Aaron
    Commented Dec 15, 2021 at 23:04

I agree that this is basically moving from IV to ii6. But instead of an augmented chord, I'd treat that A as a chromatic passing tone. If you look at the line, Beethoven didn't have any emphasis on that A. If he really wanted that to be a chord, he'd make it more apparent. An augmented chord is usually a rare case in the classical period based on how I was taught.

Haydn used it in one of his string quartets and that chord is made clear - strong beat + all notes of the chord are played.

  • The only thing is there’s an A natural on the second beat and then another one half a beat later. While they are both short, there’s two of them and if they are just passing tones why couldn’t they just be flattened as normal? Commented Dec 15, 2021 at 22:34
  • @ToddWilcox, Yes. There are two of them, but they are there for different reasons. The second A-natural is there because Beethoven needed to construct a diminished triad that resolves to the ii chord. So that chord has a function and must be constructed that way (in fact, if you change it to an A-flat, it doesn't sound as natural - or actually tonal. It would sound like a modal progression). The first A, as I mentioned, is just part of an ascending line. The sustained D-falt and F are more important than that short A, despite that it's on a strong beat.
    – lbbl59
    Commented Dec 16, 2021 at 7:28
  • The progression would become IV-I-ii if you change the second A to A-flat. Compared to the original IV-vii/ii-ii progression, that one has a plagal movement IV-I. It's a valid progression but has less tendency to move to ii.
    – lbbl59
    Commented Dec 16, 2021 at 7:41

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