I am composing a song and am used to using triads in my music with the occasional 7th chord. One problem I come across is sometimes I have a perfect 4th against a bass note and this might be an accented note. As an accented note, I don't really like the sound of this interval when it is combined with the 3rd of a major chord or against the 3rd of the minor chord. I wanted to make a list of chords that I could harmonize a perfect 4th interval and came up with these options

6/4, Sus4 and 4/2 and of course power chords which don't have 3rds.

Can someone please give me other options like these?

  • Like, you have F melody note with tonic C? Then you use a chord where the F fits. G7, F, Dm, Bdim, Bb, Db, Fm, G#dim7 for example. Or what do you mean? Apr 23, 2021 at 10:26
  • Yes, that is a perfect 4th. None of the chord suggestions you mentioned have C as the bass note
    – user35708
    Apr 23, 2021 at 10:28
  • 1
    Why do you have to have C as the bass note? Use a different bass note. Or just put C in the bass. Dm/C, Bb/C, F/C, Db/C. I really like Dm7/C, Dbmaj7/C and Fm6/C. Gm9/C works as a nice thick C7 and has an F note. Apr 23, 2021 at 10:30
  • Because I like the sound of a perfect 4th and that specific interval conveys the mood I am going for.
    – user35708
    Apr 23, 2021 at 10:47
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    But then if you add more notes it changes the mood. Voicing the chord differently changes the mood too. So you should decide what fits best for your purposes. Do you want an F/C, or a G#dim7/C, or a G7/C, or a Dbaug/C? They all contain F but sound rather different (at least to me)
    – Divide1918
    Apr 23, 2021 at 11:04

2 Answers 2


How about so what chords?

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or Gershwin‘s Porgy and Bess

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A fourth can also be part of an inversion of a b79 chord:

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  • Or, more generally, quartal harmonies.
    – user45266
    Apr 24, 2021 at 3:15
  • very nice, I hadn't heard about these before.. surprised to see so many used in a single piece. In the wikipedia page it does say that this "so what" chord could be interpreted as a Asus4-7(9) which is how I would have interpreted it but there are lots of other interpretations too.
    – user35708
    Apr 24, 2021 at 9:20

If we just accept the basic situation - a bass of, for example C and an F above, also not clear, but let's assume the key is C - the most basic treatment of that would be IV6/4 or a 4-3 suspension to a C chord.

You can grope around for other chords like ii 4/2 or IV4/3 but it's just dancing around the basic point that the harmony is subdominant.

Other options? bII4/2 which would be Dbmaj7/C, or stack up perfect fourths for G C F Bb, you could go on and on.

It might help to first think in tertian terms the C and F are either chordal fifth and root or third and seventh, then just fill in the other two tones for seventh chords and alter them for various chord qualities. What this really means is the root is either F natural or some D, natural or flat. This still means the chord will be some kind of subdominant.

But, starting down that road makes me thing we don't know what we are doing. That isn't necessarily bad if you're trying to stumble upon something new and unexpected. But that's going into territory that doesn't provide a "how-to" guide. If that isn't your intention, pick a style and follow the harmonic conventions.

...The bass rules... that is the most important note

I agree. This should mean we are thinking primarily in harmonic terms. Do you really want a subdominant? If not, the figure out what the harmony should be and then work the melody accordingly and change the F. IMO, if you have the attitude the bass rules, then work the harmony from that and then think of the melody in terms of rhythm and contour instead of a series of pitches. That is the basic homophonic approach: melody is derived from harmony.


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