The Crusade. Part 9: Secondary Dominants And Tritone Substitution

author: JoshUrban date: 02/05/2008 category: general music
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Crusaders! Here's the part you've been waiting for. So far, we've covered aspects of theory that are very textbook. In other words, you see it applied a lot, but in the real world, there's many exceptions to the rules we've viewed so far. This can be frustrating. But fear not, as we'll be learning about several things today that will clear the whole mess up. Buckle up, 'cause we've got a lot of land to cover today. Secondary Dominant Chords If you've been following the series, and have tried to analyze a chord progression, you might have gotten stuck. Perhaps something like this threw you off: (Analyze the progression) Am7 D7 Gmaj7 Cmaj7 B7 Em7 You'll remember that each key only has one dominant chord that's diatonic (built from the scale.) It's the V chord. The V chord in this key is D7, and the key is G major. The Am7 is the ii chord, the D7 is the V, Gmaj7 is the I, Cmaj7 is the IV, B7 doesn't fit, and Em7 is the vi chord. We see that B7 doesn't work because it contains the following notes: B D# F# A Compared to the G major scale: G A B C D E F# Note that the third of B7 is D#, a note not found in G major. But if you play these chords, you'll notice they sound great. And the composer knew what he was doing. So what gives? We've just encountered a Secondary Dominant Chord. In essence, a Secondary Dominant Chord is simply a dominant chord that doesn't belong in the key, but pulls to a chord that is in the key. To understand this, let's back up to what makes a dominant chord tick. If we play a D7, we sound the following notes: D F# A C Now, the 3rd, F#, and 7th, C, form the ugly sounding interval of a flatted fifth. Play 'em to hear what I mean. Hit a power chord on the 8th fret, sixth string, and move your 3rd finger down a fret, so it's on the 9th fret instead of the 10th. You'll hear how dissonant and tense it sounds. Next, move your 3rd finger up to the 10th fret, fifth string, and 1st finger to the 7th fret, sixth string. You'll be playing G and B. Note how these notes resolve the tension, and sound final. G and B are the root and 3rd of G major, respectively. If we line up the D7 and G major 7, here's what we get: D F# A C G B D F# The 3rd of D7, F#, is a half step above the root of Gmaj7. When notes are this close together, they can act strongly. In this case, the F# wants to resolve (pull) to G. The 7th of D7, C, also does the same with the B in Gmaj7. It pulls toward it. The tense interval of the flatted fifth between the 3rd and 7th in D7 pulls to the root and 3rd of Gmaj7. Play it to hear for yourself. This is how a dominant 7th chord functions, and why the V-I chord movement is the strongest progression in music. Here's the kicker. The V pulls to the I. But any chord can have it's own V chord. Let's examine this by using another chord in the key of G major. If we play a I-IV-V in G, the resulting chords are: Gmaj7 Cmaj7 D7 The D7 pulls back to Gmaj7. But poor ol' Cmaj7 is left out in the cold. Let's add a chord that will pull to the IV chord. A fifth above C is G. Playing a G7 before Cmaj7 will set up Cmaj7 nicely. Sonically speaking, it's almost like having Vanna White point to the chord- it gestures so gracefully. Examining G7, we find the following notes: G7 G B D F (which pull to) Cmaj7 C E G B (The B pulls to C, and the F pulls to E.) Note that G7 contains a note outside the key of G major - it's F natural, and the key of G major contains an F#. Playing the modified progression, we would get: Gmaj7 G7 Cmaj7 D7 The G7 could be technically be written V/IV, meaning The Five of Four (The V chord that pulls to the IV chord.) Seemingly defying the rules we've learned so far, it works beautifully to pull to desired target chords. Let's condense what we've just learned into a few basic rules: The V-I chord movement is the strongest chord progression. There's only one diatonic dominant seventh chord per key. The 3rd and 7th of the V7 chord pull to the root and 3rd of the I chord. To set up a chord other than the I chord with a dominant seventh chord, play a dominant 7th chord a fifth above the target chord. While the new chord will be temporarily out of key, it pulls beautifully to the target chord. In doing so, it could be viewed as creating it's own island key, or brief tonality change. This is technically notated V/ii, V/iii, etc. (V of ii, V of iii, depending on the chord it pulls to.) Some Application For practice, let's take a simple chord progression, and dress it up by adding some secondary dominant chords. The progression: Em7 Am7 Dm7 G7 Cmaj7 (it's a iii-vi-ii-V7-I progression in the key of C major.) To add a secondary dominant chord above Em7, we count up a fifth. (Playing a power chord from E, and looking at the second note is a cheap, but easy, way to do this.) The note is B, and our chord would be B7. Using the same logic for Am7, we arrive at E7. A7 precedes Dm7, and we'll leave the last ii-V7-I, the D-G-C, in place. Our result: B7 Em7 | E7 Am7 | A7 Dm7 | G7 Cmaj7 A Note About Minor Chords If one looks closely at the mechanisms involved in a dominant chord pulling to a minor chord, something quickly becomes apparent. Looking at the A7 - Dm7 progression, and the notes involved: A7 A C# E G Dm7 D F A C We'll see that the third of A7 (C#) is a half step away from the root of Dm7. Great, as it's as it should be. But the 7th of A7 (G) is not a half step away from the minor third of Dm7 (A.) Since the minor chord contains a flatted third, it's almost as if it misses the pull from the 7th degree of the dominant chord, as it's now a whole step away, instead of a half step. It still works, but it's not as effective as the V7 to Major chord resolution we've been looking at, which has two notes to pull. There's just one as in this example. What to do? Bring Out The Weird Chords, Baby! In particular, let's check out how a flat nine chord can get us out of our difficult situation. Let's play an A7(b9) to Dm7 change, and see how it sounds. (Pronounced A Seven Flat Nine.) A7(b9) A C# E G Bb Dm7 D F A C (In particular, we're looking for notes in the A chord that are a half step above or below the notes in the D chord.) Bingo! We now have two! C#, the 3rd of A7(b9) pulls to the root of D, and the flat nine of the A chord pulls to the 5th of Dm7. Excellent. This explains a few things. 1.) A place to use those oddball chords. They're not so weird anymore, and you can see how they serve an effective purpose. Of course, these chords come from scales, but at first glance, they appear very weird and impractical. Now you know they're not. 2.) You'll see these chords a lot in many minor progressions, such as a minor ii - V7 - I. Looking at the key of A minor, we have the following chords to work with: Am7 Bm7(b5) Cmaj7 Dm7 Em7 Fmaj7 G7 Our ii chord is the Bm7(b5), our V is Em7 and our I is Am7. Now, we've got a problem. Our V chord in a minor key is a minor chord! (Remember, the minor scale is just the major scale starting on it's sixth note.) And minor chords don't pull - dominant chords do. Why? They don't contain that interval of a flatted fifth between the 3rd and 7th that resolves down a fifth. We've gotta change that V chord into something workable. The first step is to change Em7 into E7 by raising the third. But as we've just learned the V7-minor7 pull isn't that strong. To remedy the situation, we could add a flat nine, and play an E7(b9) chord. The flatted ninth pulls to the fifth of our target chord. Groovy! (Other altered dominant chords (#9, b13, #11, etc) can do this as well, but for the sake of brevity, who I've already offended, we'll skip those for now.) Tritone/Flat Five Substitution Any conversation about secondary dominant chords invariably begs for a mention of tritone substitution. Yet another way to break out of the mold of a key while maintaining a semblance of sonic order, it is an exciting topic, indeed. (Really.) Remember how the third and seventh of a dominant chord pull to the root and third of a major chord a fifth below? Good. Here's the thing to remember: The third and seventh of that dominant chord form the interval of a flat fifth, or a tritone. I'll be using these two labels interchangeably. (Sometimes it's not correct terminology to call it a tritone in this manner, but I find it helps with the explanation.) That tritone is the heart of the chord, and it's what makes it gravitate to the I chord. Looking at the notes again: G7 G B D F Cmaj7 C E G B The notes B and F form the interval of a flat five, or tritone. See it in the G7 chord? B and F in the G7 pull to C and E in the Cmaj7. Warning: Mind Bending May Occur Ready for something odd? The chord a tritone above G7 contains the same heart or interval between the 3rd and 7th. A fifth above G is D. A flatted fifth above G is Db. The notes in a Db7 chord are: Db F Ab Cb (Cb is a disguised B.) F and B. G7 has B and F. They're just reversed, but they do the same thing. (Not all intervals can be reversed like this, but the flatted fifth is the same no matter how you look at it.) Since Db7 contains the main ingredients that make the chord move, it will also pull to a Cmaj7 chord. We can substitute Db7 for G7 in our V-I progression, and have the same motion in our music. Granted, it will sound different, but it still works. This substitution gives us two main things: 1.) A different sound. Two of the four notes are not in the key of C major! It will sound different than a G7, indeed. 2.) Chromatic bass movement. You'll notice that Db7 is only a half step above our target chord, Cmaj7! This leads a nice walk down effect, very popular with bass players. The easiest way to find the Tritone Substitution is......It'll be a dominant seventh chord a half step above the I chord! If the target I chord is Cmaj7, the substitution will be Db7. If it's Dmaj7, the substitution will be Eb7, and so on. Summary Of Tritone Substitution
  • It is usually referred to as Tritone Substitution in classical circles, and b5 (flat five) Substitution in the Jazz arena. They both mean the same thing.
  • The interval found between the 3rd and 7th in a dominant chord is a flat fifth, or tritone. This dissonant sound is what causes the chord to resolve to a chord a fifth below it. The V-I chord motion is the strongest in Western music.
  • This interval is also found in a chord a tritone away from the original dominant chord.
  • The new chord, while being outside the original key, still serves the same function, and can be substituted in to great effect.
  • The resulting sound is unique, and as the new chord is only a half step above the I chord it's pulling to, has a pleasing chromatic bass movement. (In plain English, it walks down nicely.)
  • The tritone substitution is found a flatted fifth away from the original dominant chord. This happens to be a half step above our target I chord. Much easier to remember.
  • Tritone Substitution may be used with the original dominant chord. You can use 'em both. Application Of Tritone Substitution Using our ever familiar ii-V7-I in C, let's see what we can cook up. Hey! Wake up, and pay attention! We start with: Dm7 G7 Cmaj7 Adding a Tritone Substitution: Dm7 Db7 Cmaj7 (Check out that cool chromatic line that the root notes make! D, Db, and C. Nifty!) Using both: Dm7 G7 Db7 Cmaj7 Adding Secondary Dominants A7 Dm7 | G7 Db7 | Cmaj7 (A7 is the secondary dominant, and Db7 is the Tritone Substitution.) Wrapping Up We've covered a lot today. From Secondary Dominant chords to Tritone Substitution, we've learned some pretty heavy duty theory. Let it sink in, read and re-read, and of course, try playing the chord progressions. I suggest that you print this lesson out so you can really digest it. Eat it if you have to! I do have a question, though. Who's gonna clean all the brains off the wall? Well, I certainly can't...I've, err...Got to go to lunch. Regardless of what you think, I'm not out to lunch - yet. If nothing else, I hope you've learned one thing: If you can play it, there's a theory to explain it! And - If it sounds good, it is good. Don't forget to check out my blog. Copyright 2008 Josh Urban - All Rights Reserved Josh Urban (photo) is a musician with a unique perspective on music. Always a thinker, he gains insight wherever he can find it, be it in the clubs as a working musician, busking on the city streets, or teaching in the classroom. A naturally enthusiastic fellow, Josh is always fired up about bringing the lessons he's learned to his readers. Maintaining a website, a blog, and a monthly newsletter, he aims to make musicians stop, think, and play with a little more intensity, integrity, and inspiration. You never know who's listening.
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