Tonal Theory Applied to the Guitar, Part 2: Chords, Progressions, and Cadences

author: mhillips date: 04/23/2014 category: the basics
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Tonal Theory Applied to the Guitar, Part 2: Chords, Progressions, and Cadences
First off, I want to thank you all for reading my article. I'd also like to start off with an apology. I reread part 1 of the Tonal Theory Applied To The Guitar article and noticed that I misspelled a lot of words, mentioned and promised that I would explain a few concepts that I did not, and ended the article incoherently. I'm sorry about that, however I'm hoping that this article makes up for those flaws. In this edition of my theory lesson, I plan on expanding ever so slightly on key signatures, explaining what the circle of fifths is (I probably will expand upon this more in later articles but hopefully I do it justice in this one), and I'd like to talk more about chords and how they work with each other. So without further ado, let us begin!

Recap

In part one of the tonal theory series, I explained what pitches are, how to use them to construct the four basic scales, and how to know what notes can be used in different keys. I am going to assume you either already know this knowledge and can apply it to the guitar or that you have already read my first article. If you don't know how to do this and/or you haven't read part one yet, go here and read it before continuing this article.

Circle of Fifths

In part one of the tonal theory series I talked about different key signatures and accidentals. They have concepts that are strongly related to the circle of fifths and different chord progressions and modulating to different keys can easy be done with the circle of fifths. So what the heck is it?

The circle of fifths is represented by a diagram, similarly looking to a face of a clock, where pitches, starting with C, move clockwise to a perfect fifth above the previous note.

For example, if we start on C and we follow the circle of fifths clockwise to the next pitch, the note will be a G. It will be a G because G is a perfect 5th above C. If we start on G and follow the circle of fifths in order to the next pitch, it will be a D, because D is a perfect 5th above G. This method repeats until every single chromatic pitch is represented and then the cycle will restart and loop. An interesting thing about the circle of fifths is that if you treat the first note as the key you are playing in, you can modulate to another key following the circle of fifths progression (For example if you are playing in the key of C major and you change keys to G major, or A minor to E minor).

The reason why it sounds less abrupt than changing to a random key is because the difference in the keys between two pitches next to each other on the circle of fifths is only by one accidental. For example, if we start in the key of C major, we have zero accidentals. We have the notes C D E F G A B and then C again. Now if we go up one in the circle of fifths progression to G major, we have the notes G A B C D E F# and then G again. Notice that between the two keys, the only notes that differ are the F and the F#. The difference between G and D are C and C# respectively. And so on and so fourth. Now, if you notice, all keys that have sharp accidentals will only have sharps will always contain at least F#. A perfect 5th up from F# is C#, which is the second most common sharp accidental. Do you see a pattern?

Now, let's say instead of going forward through the circle of fifths you wanted to go backwards. You would have key signatures with more flats instead of sharps. So C would move down a perfect fifth to F, which would move down to Bb, and so on. And the different between each key going down in the circle of fifths progression is by one flat (similarly to how going up adds one sharp). Instead of always having an F#, when we deal with flat key signatures, we always start with A Bb accidental. Then the next most common accidental would be an Eb because it's a P5 (shorthand for perfect 5th) from Bb.

So now you know a little bit about the circle of fifths and hopefully realize that moving in 5ths is a big thing in music. I'll mention the circle of fifths more in the future and some other concepts that relate and build upon it.

Chords

What are chords? Chords are two or more pitches being played together. Some chords can even be implied, but we will talk about that later (like probably way later). On guitar (especially electric guitar), some of the first chords we learn are power chords. What are power chords? Well, let's play a power chord having our root/tonic being our open low E string. Our chord is open on 6 (E), second fret on 5 (B), and second fret on 4 (E). If we look at our three different pitches we have an E, a B, and an E one octave higher than the first. B is a perfect fifth higher than E. Essentially, in musician talk, a power chord is a root, perfect fifth, and perfect octave.

Now let's say you aren't playing power chords (especially if you are starting out and playing acoustic guitar) and you are playing open chords. Let's take a chord that is more or less a beginners chord that's super easy to talk theoretically about: C. A C major open chord is nothing on 6, third fret on 5 (C), second fret on 4 (E), open on 3 (G), first fret on 2 (C), and open on 1 (E). If we stack our pitches we have C, E, G, C (an octave higher than the first C), and E (an octave higher than the first E). So we have a root, a major third, a perfect fifth, a perfect octave, and a major tenth. But we really only have three different distinct pitches: C, E, and G. Those notes are a root, a major third, and a perfect fifth. 

Notice that power chords contain two distinct pitches, a root and a perfect fifth, while open chords contain three distinct pitches, a root, a third of some sorts, and a perfect fifth. Power chords sound great when you are playing crunchy stuff, but the chords a naturally ambiguous. An E power chord sounds fantastic in the key of E major. It also sounds fantastic in the key of E minor. That's because all it is is a root and a fifth. The perfect fifth has an "open" and consonant sound when compared to its root and therefore is usually used to enhance the root. So if the fifth does not determine what chords have what qualities, what intervals do?

The most common interval to determine a chord's quality is the third. Thirds are present in open chords (more or less any chord besides power chords) and add a lot more flavor to chords than just fifths. However, with more pitches comes more responsibility. Thirds need to be appropriate for the keys you are playing in and the chords you are playing. If they are not, they can add a lot of unwanted dissonance.

So let's talk about the easy key of C major. If you are playing a C major chord (the first chord in the key) you are playing an E chord. E is a major third above the root of C. Thus, this makes this a major chord. Now let's say we are still playing in the key of C major but we want to go to the next interval and play a D chord. Now we have the chord D, F, and A. F is a minor third above D. This makes this a minor chord. So when we have a root, a MAJOR third, and a perfect fifth, we have a Major chord. When we have a root, a MINOR third and a perfect fifth, we have a Minor chord. So, if you notice the trend, the third of a chord determines if it has a major or minor quality. Without it (or a without a sixth, second, seventh, or anywhere else where it may be implied) the chord will be ambiguous to a specific key.

Chords in a Key

So I talked about staying in the key of C major and playing CMaj and Dmin chords just a second ago. So in a Major key we have the following chords: I, ii, iii, IV, V, vi, and viiio. I'm not sure if I touched roman numerals very well in the last article, but just in case I didn't... uppercase roman numerals mean the chord is major, lowercase roman numerals represent chords that are minor, and chords that are lowercase with with a circle next to it or the letters "dim" mean that the chords are diminished. Major chords have a root, major third, and a perfect fifth. Minor chords have a root, a minor third, and perfect fifth. Diminished chords have a root, a minor third, and a DIMINISHED fifth. A diminished interval is an interval that has been flattened by one flat. For example, a G is a perfect fifth above C. However, a Gb is a diminished fifth above C. The reason why the seventh interval chord in a major key is diminished is because of the way the scale/key is set up. In the key of C major, B is the seventh interval. The chord in the key is B, D, and F. B to D is a minor third and D to F is a minor third. B to F is a diminished fifth and thus the quality of the chord is diminished. 

About those roman numerals, remember those. Know that in any major key, your third is always part of a minor chord. Know that only your roots, fourths, and firths are major chords. Just knowing this combination can allow you to play chords and notes in any key at any time. So let's pick another simple key besides C. Let's go with G. In the key of G (G A B C D E F# G) we have the following chords (that are diatonic of course): GMaj, Amin, Bmin, CMaj, DMaj, Emin, F#dim, GMaj (repeating the first chord). In F major we would have (F G A Bb C D E F): FMaj, Gmin, Amin, BbMaj, CMaj, Dmin, Edim, FMaj (repeating the first chord again).

This knowledge is great, especially for writing new music or when improving. If you are playing with others and let's say you hear two chords. Let's randomly pick F#min and Cdim. Well, in the key of D major, Cdim is the seventh interval chord and F#min is the third. So now we know that we are playing in some form or another of D major and can mess around with the notes D, E, F#, G, A, B, and C# and it won't sound too dissonant or undiatonic.

Chord Progressions

Now, hopefully you remembered that roman numeral formula I mentioned for Major keys: I ii iii IV V vi viio. In minor keys, the formula is a little different. It goes like this: i, iio III, iv, V, Vi, viio. Notice that in minor keys, the root chord is minor, the second is diminished, the third is major, the fourth is minor, the fifth is still (in tonal music it will always be) major, the sixth is major, and seventh is diminished. So the sevenths and fifths are the same in both major and minor keys, but the 3rds and 6ths are reversed to either major or minor and the seconds are either minor or diminished.

Because of the way that chords are setup diatonically, there are certain qualities that specific chords have that relate them to other chords. For a brief example, I mentioned in the last article that the seventh interval is the leading tone. The V and viio chords both contain the leading tone interval and makes these chords want to lead into the I or i chord,

In rock and roll, the most popular chord progression is some variation of the I IV and V chords (or the i, iv, and V chords in a minor key). In jazz, the most common chord progression is some form of the I, ii, and V chords (or the i, iio, and V chords in minor). The reason why these and other similar progressions are common, work, and sound good, is because the relate to each other.

In a major key, lets start with the root. The root can move on to and play any other chord in the key. It really doesn't matter which one it moves to. The second chord can move to either the viio or the V chord. The three chord can go to either the six chord, the four, or the root. The four chord can either go to the two chord, diminished seven, major five, or the root chord. The five chord can go to either the root or the six chord. The six chord goes to either the four to two chord. The seven chord goes to the root chord. Here is kind of a diagram: 

iii -> vi -> IV or ii -> viio or V -> I

Except that V sometimes can go to vi, iii can go to IV or ii, IV can go to I, and IV can go to ii. The I chord can go to any chord in the key.

In minor keys: The root can go to any chord in the key (like in major keys). The two chord can go to either the viio or V chord (also like the major keys). The three chord goes to either the VI, iv, or iii chords (like the major keys, but with minor/diminished versions of the chords ins tea). The four chord goes to the iio, viio, V, or i chord (also like the major keys but with minor versions). The five chord goes to either the I or VI chord. The six chord goes to either the iv or iio chord. And the seven chord is interesting in minor keys. If you are playing a diminished seven chord, you go to the root, just like in a major key. However, due to the various forms of minor scales (I talked about them in the last article), the minor keys all a major seven chord to fit in the key. A VII chord that can substitute for the viio chord. This unique VII chord will only be harmonically tonal if it resolves to a III chord, Here is a diagram for the minor chord progressions: 

VII -> III -> VI -> iv or iio -> viio or V -> I

With the same exceptions in the major keys: V sometimes can go to VI, III can go to iv or iio, iv can go to i and iv can go to iio. The i chord can go to any chord in the key. And VII must go to III. So what does all this progression mumbo jumbo mean?

Let's take the key of C again and start off on a two chord (which would be Dmin). We could play chords or write a riff that is based around D minor. According to our tonal theory rules (more like guidelines but a great place to start), we can only go to either the viio chord or the V chord. Let's go with the five chord. So we have D minor and then G major. We could then eventually take the V chord to the I chord, which is C major. You could then either loop it back to the two chord and restart this progression, but if you wanted a four bar progression that changed chords every time you could then pick a chord that resolves to the two chord, like the three chord or the six chord. Let's go with the three chord. So we have Dm, G, C, and then Em. Then the progression loops. It would probably make more sense if the progression started on the Em and went Em, Dm, G, and then resolved to C. So you see, you can use these formulas to write chord progressions in a snap! You could even expand your phrases or spice them up. Let's say you wanted to expand your four bar or four chord progression to sixteen. You could play Em, Dm, G, C, and then loop it with Em, Dm, G and C. Now, loop it again but this time, instead of resolving to C, you could go to Am, which is the vi chord. That works because the V chord can go to the I or vi chords. Then you could take the vi to the IV, to the ii, to the V, and then resolves to the I. So you would have: Em Dm G C Em Dm G C Em Dm G Am F Dm G C. It is nothing too crazy but it's writing something quick on the fly that is simple enough to remember and play without too much practice (as long as we remember out theory!) and it is not too repetitive to the point where it's boring to listen to, 

Cadences

So, why is playing a six chord after a five chord more interesting than playing a one chord after a long sequence of five-one progressions? Because tonally speaking, the transition between the two chords works and is diatonic and because the five-six phrase ended differently (in the fact that it didn't end on a one chord). A cadences is a little difficult to describe, but I will try my best. A cadence is the end of a phrase or the significant part of a progression. The most basic way to end a series of chords or to end a phrase is to play the authentic cadence (there is a perfect authentic cadence and serval other variations, however I will not discuss them here. Perhaps later...). The authentic cadence is five chord followed by the one chord. So one way you could end a section of music is to go to the five chord and end at the begging of the next section/phrase on the root chord.

The authentic cadence is kind of a traditional way to end phrases. Thats way rock music uses IV V I progressions and why mass uses ii V I progressions. They both use authentic cadences to "chunk" the music into sections and to emphasize the keys the progressions are in. There are other cadences or was to get to the I or i chord (by the way, anything I mentioned above about major keys applies to minor keys as well, with the minor variations of chords and intervals and whatnot). There are plagal cadences, which is the four chord resolving to the one chord instead of the five chord. For example instead of a progression in the key of C ending with G and then C, it would end with F and then C. The plagal cadence adds a little more of a dissonant quality to the progression and is traditionally used in a lot of choral and religious music. 

There is the deceptive cadence, which I kind of discussed earlier. That is when you have a V chord that is expected to go to the root chord but goes to the six instead (like in the 16 bar progression above). It is called the deceptive cadence because usually the one chord is expected but the six chord takes its place.

Then there are half cadences, or I like to call them cliff hangers. Instead of ending phrases and progressions on one chords, you'd could end them on a five chord. It is not too uncommon to hear this and the progression sounds unresolved and half finished. Thats why they are called half cadences. Any chord to the five chord makes a half cadences, so there are several different combinations. A common half cadence in minor keys is the phrygian half cadence. That describes a progression with a minor four chord with the third of the chord as the lowest pitched note in the chord to the V chord. In this example, the iv chord is in the first inversion, but I will discussing inversions and voicing later.

I know this is a lot to memorize, but it is so usefully. Knowing what chords work in what keys and with other chords takes the guess work out of making music. Hopefully this makes some sense and should allow you to know what chords are in what keys, and where to go when you are playing over a chord and want to take the music somewhere new. If you have any questions or anything just let me know. I plan on expanding and talking about other chords like 7 chords, augmented chords, chord inversions and certain voicings. I also want to dig into rhythm, more specifics about harmony, and writing melodies. Until next lesson folks.
More mhillips lessons:
+ Tonal Theory Applied to the Guitar, Part 1: Pitches, Scales and Keys The Basics 04/25/2014
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