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Here are the first few chords of "City of New Orleans" as performed by Arlo Guthrie:

F# C# F# D#m B F#

F# C# F# D#m B F#

D#m A#m C# G#

If I lay out the chords in a roman numeral chart, starting at F#, I get:

| I  | ii  | iii | IV | V  | vi  | vii⁰ |
|----+-----+-----+----+----+-----+------|
| F# | G#m | A#m | B  | C# | D#m | Fdim |

So, in the song, he plays a G#. However, the chart predicts a G#m, which is an exception to the chart that sounds good.

Where can I read about these "exceptions"?

Thanks!

dharmatech
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3 Answers3

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The chords you've listed in your table are what we call the diatonic triads of a key. "Diatonic" basically just means "within the key," so the diatonic triads are what are created when we only use the pitches in a key's key signature.

(Quick note related to key signatures: your vii° chord will actually be E♯°, not F°, because E♯ is the seventh scale degree in F♯ major. For more on this concept, see Why do notes have multiple names?)

The opposite of diatonic is chromatic. Put another way, a chromatic pitch is a pitch that is not in the key's key signature. The G♯-major chord in question has B♯ as its chordal third, which is not in the key signature of F♯ (that would be B♮).

So whenever we have a chromatic chord like this, we want to try and understand how it functions. In many cases, the appearance of an unexpected major triad can be understood as being a temporary V (or "dominant") of another chord. In this case, the G♯-major chord can best be understood as a temporary V of the C♯ that comes before it. We say that this G♯-major chord is V/V (read "five of five") because it is V of C♯, which is itself V of the tonic F♯. We also call this chord a secondary dominant or applied dominant.

Typically the secondary dominant chord appears before its resolution; in other words, it's more normal for the G♯-major chord to resolve to C♯ major. But sometimes we have the applied dominant come after the temporary tonic, too. (It's unclear to me where this G♯ moves; it might go back to C♯!)

As for another "exception," if you ever encounter a minor chord where you're not expecting it, it's often a result of mode mixture (some use the term "borrowed chords"). (See How do I correctly borrow chords from one key to another? for one possible discussion of mode mixture. You also might enjoy What are the different ways of adding non-diatonic chords?)

TL;DR: That G♯ chord is understood as a temporary V/C♯. Since C♯ is itself V of F♯, we label this chord V/V.

Richard
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    If you've ever listened to the Foo Fighters, you've heard a major II-- Dave Grohl can't go five minutes w/o using one-- and I love it every time. – Alexander Nied Nov 08 '18 at 04:16
  • @AlexanderNied Hmm... What's an example song of theirs which illustrates this? – dharmatech Nov 08 '18 at 06:29
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    So, I actually struggled to find a place where it is clear it's what he's doing- frequently what might be a II is more aptly described as a IV in what would otherwise be a minor key but flirting in the relative major space. The two clearest examples I could find quickly were in the choruses of Walking After You on Color and the Shape and Another Round on In Your Honor. Note in neither place is it being used as an applied dominant, so the usage may be different from your song- in the former the II leads to the IV and in the latter to the vi. – Alexander Nied Nov 08 '18 at 07:21
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    I'll add that V-ii (C#-G#m) is forbidden in common practice period harmony and a rare chord progression in general from my experience. C#-G# actually makes more sense to me in an F# major context. – Dekkadeci Nov 08 '18 at 11:26
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    "It's unclear to me where this G♯ moves ... ." From my recollection (supported by the chord annotations I see online), it moves to D♯m and repeats the progression to A♯m and C♯, but this time resolves via C♯7 to F♯. – David K Nov 08 '18 at 19:23
  • I know I'm not supposed to use the comments for this. But what a clear, exhaustive answer. – Scott Wallace Nov 10 '18 at 14:49
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    @ScottWallace Better than exhausting! :-) – Richard Nov 11 '18 at 17:59
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You've fallen into the common trap of seeing a scale, and the triads that can be formed from it, as a restriction.

Yes, there is a set of chords that can be constructed from the notes of a scale. But that's no more than a mildly interesting fact. A song in a given key will use some of the diatonic chords a lot, others not so often. And other, non-diatonic chords will also very likely appear. The diatonic, scale-derived chords are not a restriction, not the chords that you MAY use. They're just the diatonic chords.

For instance, consider the C major key. C, Dm, F, G, Am will probably be used a lot. But D7, C#dim, Bb, Fm are more likely to be used than the (diatonic) B dim. And, if you're playing blues-based styles, C7, F7 and G7 are the basic chords, two of which are non-diatonic!

THE SCALE IS A FRAMEWORK, NOT A RESTRICTION.

Once you absorb this, a lot of the 'borrowing' thing becomes unnecessary. Where a chromatic chord IS used as a gateway to a modulation, there's sense in calling it borrowed. An Fm chord in C major MIGHT be a pre-echo of a Fm7, Bb7, Eb modulation to Eb. So calling it 'borrowed from Eb major' is useful. But C C7, F, Fm, G7, C at the end of 'When the Saints' doesn't go anywhere. Just let C7 and Fm be chromatic chords. 'Borrowing' them doesn't help.

Laurence
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The Ⅱ chord can serve mostly two roles:

  • A secondary dominant, as said by Richard. This would be clearly the intepretation to go if the two last chords were turned around:

    ⅵ | ⅲ | Ⅴ/Ⅴ | Ⅴ

    I wouldn't interpret the G♯ as a secondary dominant here though, if it doesn't really depend on the Ⅴ chord.

  • As a borrowed chord from the Lydian mode. The F♯-Lydian scale is F♯-G♯-A♯-B♯-C♯-D♯-E♯-. I does contain all the third line as diatonic chords. Or you might say that this entire section modulates to d♯-Dorian.

leftaroundabout
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