"Changing Keys Using Chromatic Modulation"

-Drew Peterson


 Key changes are fun. When you're writing music, there's few things quite as cool (on an 
intellectual level, at least) as jumping through harmonic hoops to get from one musical spot 
to another, and key changes can give you sonic and emotional options that are otherwise 
unavailable, musically. The problem though, is if you've never done it before, the art of 
changing keys is a fairly daunting one. So, if modulating keys is still unfamiliar to you, 
hopefully this lesson will help. 

 There's a nearly infinite number of ways to modulate keys, but a good one to begin with is 
to try to create half step movement between chord tones of your "home" key and the one 
you're moving to. Sounds a bit complex, but I'll tyr to explain...

 First, let's look at harmonic resolution itself, with no key changes. What's the 
traditional "strongest" resolution in western harmony? V7-I. In E, that'd be B7-E. So, take 
a look at the chord tones- you've got a B, D#, F#, and A, going to E, B, and G#. When you 
switch from one to the next, the B remains constant, the D# rises a half-step to E, and the 
A drops a half step to G#. The F# is also pretty tight, harmonically, either dropping a step 
to E or up a step to G#, depending on how you want to look at it... But anyway, our ear 
hears this strong tension and release because of the half-step shifts. If you want to try to
visualize this, here it is in tab:

|------|
|------|
|-2--1-|
|-1--2-|
|-2--2-|
|----0-| 

 I stripped the B7 down a bit, to root, 3rd, and 7th, but it helps you really see those 
shifts. Play it, paying attention to the top two notes... 

 So, that's how a V-I harmonic resolution works within a single key. Now, to modulate, what 
you do is apply that same principle of chromatic resolution to chords outside the key 
center. There's a number of ways to do this, but the most straightforward is by using a V7-I
resolution to resolve to the tonic of the new key. What you do is modify a chord from your 
progression to become a dominant 7th chord, treat that chord as the V7 of a new key center, 
and then resolve to that key center's I. When you changekeys by treating a chord as the 
dominant of another key, the new dominant is called a "secondary dominant" in relation to 
the primary key.( As a side note, this is actually used a tremendous amount in jazz- for 
example, the standard jazz resolution is ii-V-I, or in e, F#m, B7, E. in a jazz blues, 
rather than going from the I to the IV directly, often you'll see a progression go 
I-v-I7-IV, where the IV chord is approached with a ii-V-I progression relative to itself. 
This is, as i remember, where the term "secondary dominant" was derrived. food for thought, 
and as you get deeper into modulation, ii-V-I's will be something you want to experiment 
with- it's kinda the harmonic equivalent of quoting Shakespeare in postmodern poetry or 
something...) 

 There's a number of ways to apply this modulation strategy to a song, but the most simple 
and straightforward is to simply change the I to an I7, making it the V of what used to be 
the original key's IV, and modulating to that. In plain English, it'd be like going to A 
from E, by going E-E7-A. Johnny Cash used this to great effect in "I Walk the Line," I 
think... he changes keys a number of times, jumping by fourths ever few verses, in that 
tune.

 Of course, there's nothing that actually says the new V chord you're introducing has to 
actually be related to the previous chord changes- the resulting V-I resolution you'll be 
hearing is so strong, your ear will accept however you got there in the first place. For 
example, a modulation from A to Eb ought to be fairly jarring- A and Eb are a tritone apart, 
and their major scales (A, B, C#, D, E, F#, G# and Eb, F, G, Ab, Bb, C, and D) share only 
one common pitch (D) and no common chords. However, if you go from an A major progression to 
Bb7, the V of Eb, your ear will accept the modulation. Try it: play A-D-E-A, the I-IV-V of 
A, then play Bb7, the V of Eb, and then Eb-Ab-Bb-Eb, the I-IV-I of your new key. Your ear 
will accept it. And, as there's a whole bunch of half-step shifts between A and Bb7, this is 
actually a suprisingly pleasing resolution. 

 Additionally, you can use chromatic resolution in an almost infinite number of other ways 
to modulate keys. For example, here's another strategy- say you're in E minor. Mess around 
there a bit, maybe do an Em-Am-B7-Em to get your head into the key's tonality. Now, move to 
a G major chord. Now, play a G augmented (G+) chord- a G with a raised 5th. This is a 
horribly dissonant sounding chord, but its intervals (G, B, D#) contain one identical tone 
(D#) and two half step resolutions (G-G#, B-C) that are also present in G#, and two common 
tones (D#/Eb and G) and one half step resolution (B-Bb) present in Eb. So, try this, played 
languidly and hymnnal:

|-0-0-2-0-3--------------------------4---|
|-0-1-4-0-3--------------------------4-4-|
|-0-2-2-0-0-----4------------4-------5-3-|
|-2-2-4-2-0-------5------------5-----6-5-|
|-2-0-2-2-2---5-----5------6-----6---6-6-|
|-0-----0-3-3------------3-----------4---|

 It's actually quite beautiful, and drops you into Eb Major, a half step below your original 
tonic, and in a major, not minor modality. Granted, you could just go G-G#-Eb, but throwing 
that augmented chord in there provides a little more cohesiveness during the change (there's 
at least one common tone present between each change, from the G to G+ and the G+ to Ab), 
and the details are what make music so magical, to me. 

 Also, especially in the pop ballad world, you see modulations up a half step to a new key 
all the time- Whitney Houston or someone similar will be singing a ballad, and you'll hit 
that last chorus, where the producer wants this huge emotional climax, and the song will 
jump up one half step. Try it on a chord progression like this- strum a G-D-Em-C progression 
a number of times, to really get the sound of the harmonies into your head. Once they're 
secure there, then start playing G#-D#-Fm-C#. The effect is this big uplifting harmonic 
rush... It's pretty cheezy, but it works. It's a bit of a pop cliche, but you still see it 
in "real" music- Blues Traveler goes from A to Bb to B in the last two choruses of 
"Optimistic Thought" off their Travelers and Thieves album, for example. 

 Anyway, there's a number of other ways to approach modulation- Satriani's "Pitch Axis 
Theory" is another notable one- but modulating by looking for shared chord tones and 
chromatic resolutions is a great way to get started. I've only really hit the tip of the 
iceberg here- for example, half the fun of secondary dominant modulations is in finding 
substitutions for the V7 chord- try a iivdim or a ii in it's place, as a starter; chords 
that share a number of tones with the V7- and then there's a seemingly infinite number of 
other ways to approach a I chord aside from the V. Just remember, the modulations that will 
sound more "in" to your ears are the ones that rely on common tones to connect the chord 
changes, that provide a certian amount of "connection" between the two keys. It's like 
telling a story that has two settings- you as the performer/composer simply need to show a 
relationship between those two settings, that explains how you got from one to the next. It 
doesn't matter how- you could walk, you could take the subway, you could fly, whatever- it 
just matters that you ARE able to show a path from one to the next. 

 Of course, the best advice I ever got on this when I was struggling with the same ideas 
came from my music professor up at Middlebury, Su Lian Tan. She told me she had the same 
problem when she was studying composition on the piano as a kid, and her teacher told her, 
"when you want to go from one key to the next, just do it; the music will sort itself out." 
Don't be afraid to experiment and try things that shouldn't work, because at the end of the 
day, what your ear is telling you matters far more than what your knowledge of theory is 
telling you. If you can get it to work, then that's enough, and the music will speak for 
itself. Good luck!