This is an intermediate lesson on borrowed chords. This lesson assumes a working knowledge of tertian harmonization, keys, the connection between scales and chords, and progressions. (If you've been working from the beginning, you should be ok if you pay close attention. If not, you could start at http://simianmoon.com/snglstringtheory/chords/index.html and work your way through any material remedial to this point).
the major scale (W-W-1/2-W-W-W-1/2; 1,2,3,4,5,6,7) can be harmonized in 3rds to give the following chords: I-ii-iii-IV-V-vi-viio (in triads), and Imaj7-ii7-iii7-IVmaj7-V7-vi7-vii7b5 (in seventh chords).
Placing this key into a key context, we say that the C-major scale (C,D,E,F,G,A,B,C), can be harmonized to give the following chords: C-Dm-Em-F-G-Am-Bo, and Cmaj7-Dm7-Em7-Fmaj7-G7-Am7-Bm7b5.
These chords tell not only which chords are harmonized by the major scale but also by omission which chords are not found in the major scale.
We can create progressions from chords only found in the major scale (in a major scale context), or randomly put together with no context, or from a different scale or somewhere inbetween. It's that somewhere inbetween that we look into today.
Consider the G-major scale (G,A,B,C,D,E,F#,G) and corresponding triads and 7th chords: G-Am-Bm-C-D-Em-F#o; Gmaj7-Am7-Bm7-Cmaj7-D7-Em7-F#m7b5.
If we rearrange the chords from the C-major scale to start at G, which would look like a harmonization of the G-Mixolydian scale, we get: G-Am-Bo-C-Dm-Em-F; G7-Am7-Bm7b5-Cmaj7-Dm7-Em7-Fmaj7.
We consider the idea of the borrowed chord.
We can take a chord from one system and place it into the other system and preserve functionality. This is sometimes called "modal mixture".
G-maj = G-Am-Bm-C-D-Em-F#o (Key of G-maj)
G-mix = G-Am-Bo-C-Dm-Em-F (Key of C-maj)
G-min = Gm-Ao-Bb-Cm-Dm-Eb-F (Key of Bb-maj)
Consider progressions like:
They are combinations of chords from the above 3 systems, and preserve the functionality, and the tonal center.
So, one use for borrowed chords, would be as a method for creating chord progressions.
An early valid use is in looking for inside choices while analyzing music. It is helpful to find rationales for why some music seems to work when it doesn't fit into a simple scheme.
let's look at the above 3 progressions, and consider some simple possibilities for soloing over the chord changes.
G,F, and C in a row suggest G-Mixolydian (or C-major), while C-D7-G suggest G-major.
Ao and Cm suggest G-minor (Eb-major) while D and G suggest G-major.
G,Bm can be found in G-maj; F,Am can be found in G-mix (C-maj), as well as F-major (if you look at it as a parallel repetition of the 2 previous chords). Am-D-G suggest G-maj again.
The previous examples all come from systems based on major scales and their modes that contained the same pitch in them somewhere. This need not be the case though. We could have borrowed chord progressions that :
A.) come out of more than 2 scales,
B.) come from scales other than a major scale (or its modes),
C.) Come from a scale that doesn't include the root note of the other scale.
Next lesson is on passing chords.
How do I change all those numbers to letters (for notes, chords, etc.)? Here's a transposition chart simianmoon.com/snglstringtheory/guitar/8theory3.html
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