I'm trying to analyze a song I recently discovered, "The Chamber of 32 Doors" by Genesis. Here is the song link:

At 1:02, there is a chord progression with a descending chromatic bass line. The chords of this section are: C#m G#/B# Bm F#/A# F#m/A F#°/A G# C#sus4 C#

I would analyze the chords the following way: c#: i V6 iv/iv IV6 iv6 ??? V I(5/4-5/3).

I'm not quite sure how to analyze the F#°/A chord. Is there a way to explain how this chord is functioning and where it "comes from"?

I'd appreciate any thoughts on how this could be analyzed from a theoretical perspective. Thanks in advance!

  • 1
    Diminished chords are often hard to place. Since every note is m3 from the next, it depends on the key, but also what the bass note might be. I've seen the same note diminished chord labelled in two different ways in the same song, for no obvious reason.
    – Tim
    Commented May 26, 2020 at 10:24

1 Answer 1


Very interesting! As Tim commented, diminished chords are somewhat ambiguous by design: notice that F#°7, A°7, C°7, and D♯°7 are all enharmonic equivalents.

I would analyze your chord as vii°7 in the key of C♯ minor, inverted to have A in the bass, and with the note D♯ omitted.

D♯ can be considered the least important note in this chord because vii°7 is itself a substitute for V7 (here G♯7) in which the fifth is often omitted. The note D♯ is also used extensively in the melody.

  • Thanks very much for the response! I hadn't considered it being a chord with a note omitted, but that definitely makes a lot of sense to me. Always fun trying to find ways to explain the music that we love! Commented May 27, 2020 at 2:23

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