I've been studying Jazz for some years now, and when I come upon a chord like Abm (b5), I play a diminished chord.

But recently, on the classical harmony I'm studying, I came upon this exercise:

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On the fourth bar, there is a Ab, and on top of it, (the figured bass) is 5b.

Does this refer to a perfect fifth, which is a Eb or a diminished Ab Chord?

  • The flat 5 voicing isn't quite a diminished chord. The 3 is left as a major3, and the 5 is flattened. In diminished, both the 3 and 5 are flattened, so the sound isn't the same.So - Cb5 = C E Gb. Co = C Eb Gb for triads.
    – Tim
    Apr 7, 2015 at 10:02

2 Answers 2


It's just to let you know the when building the chord you don't use the 5th that is natural to the key, but a lowered one instead. Remember every figured bass marking assumes you are building your harmony inside the key you are in and in this case you are not.

So the figured base is referring to Eb instead of E as that is what a standard 5 would represent.


It refers to an interval of a fifth. The b is for you to know that the note should be flat by the key signature. Don't think these symbols as chord symbols. Think of them as intervals regardless of quality (i.e. major, minor, perfect etc.) from the bass note. If an accidental is required it will be given as in your case. The same goes for every other accidental symbol.

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