diatonic modulation / changing keys

When the music changes key centers, theorists refer to this process as "modulating from one key to another." What role does modulation play in the various styles of American music? Well, all of the popular styles of American music modulate at some point to some degree, some of the styles just more than others. While the majority of popular compositions start, stay and end in the same same diatonic key, we do often hear things modulating, especially towards the end of the arrangement. For the most part, it is in the world of American jazz music where the changing of tonal centers within one composition is so common. Where the harmony of folk, blues and rock move from chord to chord, jazz music often moves from key to key. Example 1.

So what's the difference between the two different tonic to Four chord motions? Well the jazz one is a cadential motion that defines the F major 7 chord as a tonal center, thus we've modulated or changed keys. Although this sorta seems kinda like splitting hairs, when improvising melodic lines it makes a lot more sense. So, whether due in part to the faster tempos of the jazz, or that one melodic idea is often repeated over different harmony, we find the modulation of keys as an integral part of the jazz vocabulary. Ever hear the jazz mantra about running an idea through the 12 keys?

Is modulation also a part of the larger musical form that we use to write songs in the American styles? Compositionally, pairing two or more key centers in one piece of music presents some unique challenges for the writers and players and some nice rewards for the listeners. And even though some of the most adventurous jazz of our day might modulate from our starting key to the far distant realms of tonality, 9 out of 10 of these songs returns back to the home key to complete the journey. Is there any popular American tune that starts in one key and ends in another?

The discussions concerning modulation which follow are structured upon the 7 diatonic degrees of the major scale. Each degree is examined for it's modulation potential, staying roughly in the diatonic realm. A second page follows which takes up some of the more common modulation possibilities outside of the diatonic realm. Although there is potentially a bit of theoretical gray area in regards to whether the following musical ideas have genuinely modulated from one key to another, the ideas being only three or four bar phrases in these following examples, if a tonic chord is preceded by it's dominant, we've modulated. The resolution of tritone tension within the dominant chord becoming the determining factor. Thus initially at least, perhaps the easiest way to "theoretically" set up a modulation to or towards a new key in either the major or minor tonality is simply to sound the dominant or Five chord of our tonal destination. So anytime we want to change keys, we can just play the V7 chord of the key we want to go to? Exactly. Do we always have to have a Five chord to modulate? Of course not, this is American music, there are no rules. Artistic responsibility and integrity? Yes. Rules? Well ...

One / tonic. With music written in the major tonality, the first degree of the major scale is usually designated as the tonal center, providing the root or fundamental pitch which becomes the center of tonal gravity of the music. One way common motion of the tonic is in the modulation to the subdominant or Four chord. In this diatonic modulation, our tonic chord simply takes on dominant qualities, becoming a secondary dominant pivot chord and moves by perfect fourth to Four. Example 1.

Sound familiar? This motion from One to Four is very common in many styles of American music. Could very well be the most popular modulation of all times. Check out Errol Garner's classic jazz standard "Misty" to hear the above idea. "Four" by Miles Davis uses this modulation to dramatic effect. Check it out when time permits. In writing tunes, so often our main theme is simply restated on the subdominant.

Two. On the second degree of the major scale, we can alter the diatonic Two minor 7 chord to dominant 7th and modulate to the dominant or fifth scale degree. Example 2.

This modulation establishing the dominant as a new tonal center with the piece is very common in older European classical music, especially within the sonata / allegro form.

Three. The minor tonality provided by the third scale degree within the major scale is a reasonably popular tonal destination. Here we alter our diatonic half diminished 7th chord to a dominant chord type and move to Three, changing from the major tonality to the minor along the way. Example 3.

The tender and loving jazz ballad entitled "My One And Only Love" by Guy Wood and Robert Mellin pairs these two key centers to startling effect.

Another perhaps more common modulation using the Three chord is to move to the relative minor of our tonic C major. We simply can morph the diatonic minor 7th Three chord by raising it's third by half step to create a dominant type chord, enhancing the cadential and modulating direction to the relative minor key. Example 3a.

George Gershwin's classic "Summertime" pairs these two key centers. "My Romance" by Rodgers and Hart uses the relative major / minor pairing to support the development of one melodic idea through the A / B 32 bar form. Pairing the relative major / relative minor keys within one composition goes way back in the history of music.

Four. Modulation from tonic to the fourth scale degree is as common as it gets in the diatonic realm, in all of the American styles. Here we simply slip in a passing Two chord and morph our tonic major 7 chord into a dominant type chord, then move by perfect fourth into the new key center. Example 4.

Check out "God Bless The Child" by Billie Holiday to hear the above motion in action.

Five. Modulation to the fifth scale degree is fairly common, especially in the sonata / allegro from or earlier European classical music. Here we use the altered Two chord within the common Two / Five / One chord progression to set up the modulation to the dominant of our tonic key. Example 5.

Six. On the sixth scale degree we can locate the relative minor tonality. Modulation to Six is very well perhaps the most common of diatonic modulatory destinations. Example 6.

In the above idea we create the deceptive cadence by using the diatonic Five chord moving to the minor Six. Clearly modulating from relative major to relative minor in a modal sort of way. Another possibility is to use an altered Three chord, as done in example 3a above. Of course, we can easily go in the other direction from the minor Six Aeolian to the major One Ionian via the diatonic Five chord. Example 6a.

Again, pairing relative minor / relative major is quite common in most of the styles of American music.

Seven. On the seventh scale degree, we oftentimes alter the diatonic half diminished Seven chord to a dominant quality and move to the minor tonality based on Three. Example 7.

What might be a common motion after modulating to Three? Motion to Four?

Well, have an idea of the term modulation and what it potentially implies? Again, modulation is not all that common a compositional technique in folk, blues and rock writing, but in the world of jazz, modulation plays an important role in the creation of the music. Not only do we commonly encounter motion from the major tonality to the minor and visa versa, but to virtually any of the tonal centers available. Perhaps I'm making a bit too much of a fuss about the motion of say One to Four as in example 1 above, but understanding the basic idea of modulation can open up some pretty big doors, not only in composing or hipping up an arrangement of non modulating tunes, but in making the transition from a blues / rock basis into the world of jazz music, where changing keys is so common and the understanding of which so potentially important to the development of one's artistic voice.

All of the above ideas are based closely within the confines of the C major tonality. We can dramatically expand the possibilities by simply expanding the resource to include any of the 12 major or 12 minor keys as created from the chromatic scale within equal temperament. Shall we? Simply click modulations / non diatonic destinations.

Each of us must work for our own improvement, and at the same time share a general responsibility for all humanity. Marie Curie