First of all, let's get acquainted with some terms, as well as some other aspects of key signature theory. The most common of all progressions would be the I-IV-V idea. In the key of C the chords are: C (I), F (IV), and G (V). The one (I) chord is built upon the root note, otherwise known as the tonic. If you count up diatonically (diatonic means notes within the key signature, for example, in C major: C D E F G A B) to the fourth note you find the four (IV) chord, also known as the subdominant. The five (V) chord is called the dominant. A dominant chord wants to resolve down a fifth, especially when it is a dominant seventh chord, like a G7 in the key of C major.
A secondary dominant is a form of a substitute chord. It may contain notes which are not in the key signature, and it wants to resolve to a chord other than the tonic. It is often refered to as a V of something, with the something being the chord that the secondary dominant wants to resolve to. The most common secondary dominant is the V of V chord. In the key of C, the V of V chord is a D major, the V of G, and will usually be a D dominant seventh chord. The D dominant seventh chord has the notes D, F#, A, C. Notice that the F# is not in the key of C major. This creates tension and adds tone color that you cannot find when adhering only to the notes within the key.
The mediant is the third tone of the ascending diatonic scale, an E in the key of C. The chromatic mediant is the flatted third scale degree, or an Eb in the key of C. The chromatic mediant chord in the key of C is an Eb major. This can be used as a substitute chord, and it can also be used for modulation. Modulating is the act of moving harmonically from one tonality (or key) to another.
A borrowed chord refers to a chord which is "borrowed" from the parallel major or minor key. The parallel minor key to C major is C minor. Yep, it's that simple. A common example of a borrowed chord in a major key is the iv, or minor four chord, an F minor in the key of C. As you may have noticed, capitalized roman numerals refer to major chords, and lower cased numerals refer to minor chords, using classical music theory.
Along with parallel major and minor keys, there are relative major and minor keys. Parallel keys share the same tonic, or root note (like C major and C minor). Relative major and minor keys share the notes in their key signatures (like C major and A minor). This is also useful for modulation, as well as building and releasing tension. Some songs ambiguously dance around the relative major and minor keys untill finally resolving to the tonic of the major key.
A substitute chord is a chord which is similar enough harmonically to be substituted for another chord. As mentioned above, these can include chromatic mediants, secondary dominants and borrowed chords, but they can also be other chords from within the key signature. The ii chord can be a substitute for the IV. These chords are very similar. The ii chord in C major is a D minor, and the IV is an F major. Look at the notes in these chords: Dm has D, F and A; and the F major has F, A and C. Two out of three notes are the same. Other substitutes include: iii for I, vi for I, and iv for IV. They all have two notes in common.
All right, now let's look at some examples! To play these examples you'll need to know some common chord shapes. Also note that everything within these symbols, ||::|| is a repeated idea, and that // means that the same chord is played as was in the previous measure. Send me a message if you're struggling and I'll be glad to help you out.
Here's a short progression utilizing a secondary dominant. 4/4 time.
||:C |Dm |F |G |Am |E7 |F |G7 :||
The G (or V chord) in measure 4 does not resolve to the tonic, but rather proceeds to the vi. The vi is a substitute for I, so it sounds nice but unresolved. This is also called a deceptive cadence. Measure 6 is the secondary dominant, a V7 of vi, but instead of going to a vi chord it goes to a IV (IV is a substitute for vi, as well as vice versa). This is great tension. Try replacing the E7 with an E minor. Notice the difference in tone color. Both are cool progressions, but the G# in the E7 adds a subtle bit of "spice".
Now a short progression using the chromatic mediant. 3/4 time.
||:C |D7 |Ebmaj7|F :||
The D7 in mm. 2 is a secondary dominant, a V of V. The iii is a substitute for the V chord, and the chromatic mediant is a substitute for the iii. Keep in mind that a substitute chord does not have the same function as the origional chord. Try replacing the Ebmaj7 with a G and you'll see what I mean.
Here's a quick example of how to use the cromatic mediant as a modulation for a bridge or chorus. 3/4 time. The numbers refer to the measures. (It's in E to utilize more open chords)
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16
||:E |B7 |A |Asus2 |E |B7 |A |Asus2 |G |D |Am |C |G |D |Am |B7 :||
When we get to mm. 9 it's a direct modulation to the key of G. G is the chromatic mediant of E. We cycle through a similar progression in G untill mm. 16 when we modulate back to E using the B7. The B7 is the V in the key of E, but it could be a V of vi in the key of G. This is called a pivot chord. These do not seem like closely related keys, but the chromatic mediant is not foreign to our ears so it sounds good.
Here's a progression that's ambiguously in both it's relative major and minor keys. It's in 4/4 time.
||:Am |G |F |G |Am |C |F |// |Am |G |F |G |Am |C |F |// |
||C |// |F |// |C |// |G |E |Am |G |F |G |C |// |// |// :||
Technically it's probably in C major and begins on the vi chord, but you can feel the pull to A minor is very strong. That's especially evident when you repeat the entire progression. When it wraps back around to that A minor, it feels like home, and that's what the tonic should feel like. On the other hand, it could easily end on the C. Tons of songs modulate to the relative major/minor for a chorus or bridge.
Here's an example of what I like to call playing in a minor key with a borrowed I chord. It's in the key of A to utilize open chords. 4/4 time.
||:A |C |G |F |A |C |Dm |E :||
Notice that all the chords are in the key of A minor except for the I which is a major chord (The V chord in a minor key is often a major chord even though the key signature does not suggest it, this is the only other exception). Play the progression with A minors instead and notice the subtle difference in tone color.
Now here's a standard slow blues progression that has been used in countless songs. It is in 6/8 time. The numbers refer to the measures.
1 2 3 4 5 6 7 8 9 10 11 12 13 14
||:C |C7 |E7 |// |Am G|F Fm|C |A7 |D7 |G7 |C C7|F Fm|C |G7 :||
Let's analyze it by measure:
- That's the root or tonic chord.
- Look's like the tonic, but it's really a V of IV. It's a dominant seven chord so it can't be a tonic, that would be a major seven chord. Notice that it does not resolve to the IV chord, but rather goes to the V of vi. This is creating tension.
- V of vi chord. Nice and tense, sounds real cool.
- Same chord
- vi chord, releases some tension. V chord, rebuilding the tension. The V wants to resolve to I, but we're not going to let it.
- IV chord. Borrowed iv chord (from parallel minor), isn't it beautiful?
- I chord, finally release all that tension.
- V7 of ii. Real tense chord because of the C#, one half step above the tonic.
- V7 of V (substitute for ii).
- V7 chord. Measures 8-11 are also known as a VI II V I progression. This is called a circle of fifths progression because each chord is a perfect 5th below the previous chord. The tension is big because these are all dominant seventh chords.
- Give me that tonic! However, before we have a chance to enjoy it, the tension is building again. V of IV chord.
- IV chord. Notice the difference between going from the V of IV to the V of vi in mm. 3 versus resolving the V of IV to the IV in mm. 11. Borrowed iv again.
- Tonic chord, but not completly resolved. All those borrowed chords have created instability within the key.
- V7 chord. Re-establishes the key tonality.
So now start spicing up some of your own chord progressions with substitute chords! It's a good idea to learn the rules of music theory, to understand the relationship between tonal centers, the way secondary dominants effect tone color, and the way modulation can breath fresh life into a chorus or bridge. Study lessons here at WN and wherever you can find them, analyze progressions that you find interesting: everything can boil down to theory. However, theory does not make good music, good music makes theory. Remember what theory is: it's the branch of a science or art that deals with it's principles or methods, as distinguished from it's practice. Eventually all of that fades away and you're left with an ability to effortlessly express the music inside your mind.