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More key confusion

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(@zaiga)
Trusted Member
Joined: 19 years ago
Posts: 64
Topic starter  

OK, instead of trying to answer questions about keys, let me ask a question about it myself. I wrote a song with the following chord progression. Below it I have written the melody line.
D . . . C . . . Fm . . . G . . .
d e f d

Cm . . . D . . . Fm/C . G/B . Cm . . . .
c d b c

So, what key is this in? Purely looking at the melody line I'd say C major. The chords however suggest C minor with the Cm acting as the i chord. Or is it C harmonic minor, as the V chord (G) suggests? Or am I now confusing scales with keys? What's the difference between a scale and a key anyway?

In any case, the chord progression would be written as:
II - I - iv - V
i - II - iv - V - i

Right? Anyone care to shed some light on this?


   
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(@noteboat)
Illustrious Member
Joined: 21 years ago
Posts: 4921
 

'Key' has a bunch of different meanings: Key signature, root tone of the scale, scale used, or harmonic progression. Since it has so many meanings, a clear-cut answer isn't always possible, and one piece can be seen in two different 'keys' depending on which meaning is intended. Yours is a good example of this.

First look at your melody notes: B-C-D-E-F. You are probably in the key signature of C, since the sharp keys include at least an F# note, and the flat keys include at least a Bb note.

Now look at the notes used in your chords: Ab-A-B-C-D-Eb-E-F-F#-G. That's ten notes... and no single key will have more than seven (for major keys) or nine (for minor keys when the melodic minor is used).

So you're either changing keys, or making substitutions from outside the key. Analyzing something like that can be complicated, but it can be done.

Look at the chords you use... three major chords: C, D, and G. Those will be the I-IV-V in the key of G, or the II-III-VI in the key of Bm, relative to D major.

In the key of G you'd have: V-IV-vii-I-iv-V-vii-I-iv
and in Bm: III-II-v-VI-ii-III-v-VI-ii

Not very satisfying. No cadences in either one. So let's look at the keys on either side: A and C. We'll reject A right away - the C, F, and D in the melody won't work... and if it's Am, well, that's relative to C anyway.

In C: II-I-iv-V-i-II-iv-V-i

Now we're getting somewhere. Two V-i cadences, and a i-iv-V set, making C minor a strong possibility. That would mean you're borrowing C major for the second chord - a logical choice, since the E in the melody is raised, and you'd switch to a major chord to harmonize that.

Cm is relative to Eb major, with three flats: Bb, Eb, and Ab. No A notes in your melody, only 1 E note (with a borrowed chord), and the B natural would be from the harmonic minor mode - which also explains the G major chord as V.

All we have to explain now is the II chord. We'd expect to see Dº in the natural or melodic minors, or Dm in the ascending melodic minor. So you've done a substitution of D... and that makes perfect sense.

One of the things you can do in composition is to move between chords of the same type even if they are not in the same key. It might not sound traditional, but it won't sound bad - just listen to "Sitting on the Dock of the Bay", which uses only major chords - on all seven scale tones!

In fact, since you've borrowed the parallel I chord for C, using a D major chord gives you a more natural flow... two consecutive major chords, then the segue to the parallel minor.

So your key is C minor. You're using the harmonic minor scale, with a raised third (and a borrowed harmony to go with it) in the beginning of the piece. But since the only accidentals you need for the harmony are Ab and Eb, you might want to write it in the key signature of C - key signatures and keys usually match, but it's not written in stone that they must... the purpose of a key signature is to make the music easy to read, with as few accidentals as possible; it has little to do with harmonic analysis.

Guitar teacher offering lessons in Plainfield IL


   
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(@anonymous)
Illustrious Member
Joined: 17 years ago
Posts: 8184
 

Look at the chords you use... three major chords: C, D, and G. Those will be the I-IV-V in the key of G, or the II-III-VI in the key of Bm, relative to D major.

In the key of G you'd have: V-IV-vii-I-iv-V-vii-I-iv
and in Bm: III-II-v-VI-ii-III-v-VI-ii

Not very satisfying. No cadences in either one. So let's look at the keys on either side: A and C. We'll reject A right away - the C, F, and D in the melody won't work... and if it's Am, well, that's relative to C anyway.

In C: II-I-iv-V-i-II-iv-V-i

I'm just trying to figure out the order of how you derived to C.

"So let's look at the keys on either side: A and C."

Why are we looking at the A, again?


   
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(@noteboat)
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Joined: 21 years ago
Posts: 4921
 

Well, we looked at G (1 sharp) and Bm (2 sharps) first, and those didn't work. But it doesn't make sense to just try random keys... there was a reason I started with G and D/Bm, so a nearby key makes more sense to try next... and the nearby keys are C (0 sharps) and A (3 sharps)

Guitar teacher offering lessons in Plainfield IL


   
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(@anonymous)
Illustrious Member
Joined: 17 years ago
Posts: 8184
 

OK - I got it, now. I'll remember to draw the circle of fifths next time, so I don't get confused. :lol:


   
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(@zaiga)
Trusted Member
Joined: 19 years ago
Posts: 64
Topic starter  

So your key is C minor. You're using the harmonic minor scale, with a raised third (and a borrowed harmony to go with it) in the beginning of the piece. But since the only accidentals you need for the harmony are Ab and Eb, you might want to write it in the key signature of C - key signatures and keys usually match, but it's not written in stone that they must... the purpose of a key signature is to make the music easy to read, with as few accidentals as possible; it has little to do with harmonic analysis.

This makes perfect sense to me. Thank you very much! :)


   
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