The Crusade. Part 7: Analyzing A Chord Progression

Today we'll be mounting an assault on the formidable enemy called Ignorance, to be sure.

Ultimate Guitar

Greetings, noble and brave Crusaders! Today we'll be mounting an assault on the formidable enemy called Ignorance, to be sure.

We call it Operation Lock pick.

The mission? Figuring out the key of a song!

John, Joe, and Derick have written a new song, and Joe needs to play a blazin' solo over it. But he's not quite sure what is what, and which scale he should use over the chords of their latest song.

Sound familiar? Fear no more, Joes of the world! This lesson will help you conquer keys, or at least take a good bite out of 'em.

So let's get into it. Pull up a chair, put on your thinking cap, and get ready to start applying the knowledge you've worked so hard to understand. Soldiers, time for action!

Before We Start

I've received a lot of questions about how to use the minor scale. A source of general confusion, especially among the metalheads who want to sound spooky and are suspicious about the major scale. After all, it sounds a bit too church, and not enough Metal Church! Not cool. Keep this in mind: While the lessons are presented using the major scale for continuity's sake, the same concepts hold for the minor scale. The minor scale is simply the major scale starting off it's sixth note! If the order of the seventh chords in a major scale are (written in C major):

Cmaj7 Dm7 Em7 Fmaj7 G7 Am7 Bm7(b5)

The relative minor scale, or minor scale that shares the same notes and chords, would start off the sixth note, A, in this example. And the order of the chords would be as follows:

Am7 Bm7(b5) Cmaj7 Dm7 Em7 Fmaj7 G7

Exactly the same, just in a different order. Now, on to business.

The Song

Let's use an example based loosely on the jazz standard Autumn Leaves. The chords are slightly different for instructional purposes (the Bm7 is actually a B7 on the chart from The Real Book, but we'll take liberty for the sake of liberty - of our minds!).

Am7 | D7 | Gmaj7 | Cmaj7 | F#m7(b5) | Bm7 | Em7

De Constructing A Puzzle

What is the key of this song? Is it determined by the first chord, A minor? Not in this case.

By the last chord? Sometimes. Here's the long, involved, boring, important way to figure it out.

The Long, Involved, Boring, Important way to figure it out.

Let's start with Am7. If you haven't read The Crusade - part vi do it now before you read any further. And that's an order, soldier!

Am7. We know that any minor 7 chord can be built from the ii, iii, or vi degrees of a major scale.

Let's do the math, and see what three scales this Am7 chord could come from. Don't worry if this seems next to impossible at first. It gets a heck of a lot easier once you do it a few times.

Am7 could be the ii chord of G major.

(G A B C D E F# ) Note how A is the second degree of the scale, and if you built a chord from that degree, you would end up with an Am7.

Am7 could be the iii chord of F major.

(F G A Bb C D E ) A is the third note of the F major scale, and likewise if you constructed a chord from it, you would end up with an Am7 chord. The iii chord of any major scale is always a minor chord.

Am7 could be the vi chord of C major.

(C D E F G A B) A is the sixth note of the scale, and Am7 would be the resulting chord built on that degree.

So far, we have three possible keys. The Am7 chord could be the ii of G, the iii of F, and the vi of C.

Let's do the same for the other chords, and a key should emerge.

The Dead Giveaway

D7. We know from the last installment of The Crusade that there's only one dominant seventh chord per key. Moreover, the dominant seventh chord is always the chord built on the 5th note of the major scale. What major scale has D as the fifth note? Counting backwards from D, while sounding like preschoolers, we get:

D C B A G.

D7 is the V chord of G.

A Pattern Starts To Emerge

Ah ha! In our list of possible keys for the Am7 chord, G major is mentioned. There's a key that both chords share, G major. But, let's make sure.

Other Chords

Gmaj7 Two major seven chords are found per major scale. The I chord and the IV chord. Gmaj7 could be the I chord of G major, or it could be the IV chord of D major (D E F# G A B C#). Since we're gunning for the chords to fit in G now, it checks out OK.

Cmaj7 could be the IV chord of G (G A B C D E F#), or the I chord of C.

F#m7(b5) This little bugger, like the V7 chord, is only found once per scale. It's the vii chord of the major scale. Keeping our fingers crossed, let's figure out what the seventh note of the G major scale is.

G A B C D E F#

Bingo, it checks out perfectly. F#m7(b5) is the vii chord of the G major scale.

Bm7 is the possible ii chord of A major, the iii chord of G major, or the vi chord of D major.

Last, but not least, our Em7 chord. Em7 could be built from the ii, iii, or vi notes of a scale.

It could be the ii chord of D major, iii chord of C major, or vi of G major.

Adding 'em Up

Let's add up the possible keys, and see what pattern emerges:

Chord Possible Key

Am7 F, G, C

D7 G

Gmaj7 G, D

Cmaj7 C, G

F#m7(b5) G

Bm7 A, G, D

Em7 C, D, G

We see that G is the only key that is common for all of our chords, so G major it is. This method of determining the key can be used anywhere. Sometimes, especially in certain jazz songs, the key will change! Keep this in mind when puzzling through chord progressions.

How It Falls Out

We've got the key. We've got the chords. Here's how it falls out. The chords are charted, and their function (ii chord, iii chord, etc) is plotted below.

Am7 | D7 | Gmaj7 | Cmaj7 | F#m7(b5) | Bm7 | Em7

ii V7 I IV vii iii vi


If the key of the song is discovered, in this case, G, then you can use the G major scale and it's related modes to solo over it. In more detail, G Ionian, A Dorian, B Phrygian, C Lydian, D Mixolydian, E Aeolian (Natural minor), and F# Locrian. Keep in mind that this is a very basic view, and certain notes of certain scales won't sound too hot over certain chords. But all of these are in key.

What about arpeggios? A very good choice, and you could use the arpeggio of each chord to construct lead lines or killer sweeping passages. Rock on! Arpeggios, commonly associated with Erik the Red and spandex, are actually used to great effect in jazz. A fantastic way to link your improvisation to the song, reflecting each chord with one or more of it's tones is called playing the changes. Harder than it looks, it sounds nifty, and it's well worth the effort.

What if the key of a song changes? Simply change your scales accordingly! If the key changes from G to C, you would do the same with your modes, switching them from G to C.

A Few Notes

Different musicians may approach this process of finding the key in a variety of manners. A very useful method is to write the notes of each chord, and figure out a common scale, and therefore, key, in that way. Others may use a more strict chord/scale view, which we'll be examining in the future. The important thing to remember is that there is no one right way to do things, especially when it comes to theory. The way presented in this article works well for me, and it's what I use. But if you find a different way, that's super, and I encourage you to use what works best for you.


Now's the time for action! Grab some of your favorite songs, and try to analyze the progressions. Figure out what key they're in. And feel free to drop me an email to grade your homework! is where you'll get answers - they may be slow, but you will get 'em! And a word of warning. A song usually doesn't fit as neatly into a key as you would like. Remember, at the end of the day, theory is just an approximation of what takes place in a song. And if it sounds cool, there's probably a theory to explain it.

There's chords that come from parallel scales, secondary dominant chords, non-functioning dominant chords, substitutions, and an entire zoo of theoretical creatures great and small. Have no fear, we will learn about all of 'em.

Pentatonic Junkies

We've taken this modified version of Autumn Leaves, and determined that it's in the key of G major. The relative minor of G major is E minor. If you've just gotta play a pentatonic over this, E minor pentatonic would be your first choice, although others will work. Dig?

The Special Case Of Blues

We've learned the formulas, we've studied hard, and we're just starting to get the point when...We try to analyze a blues progression. A blues progression, unlike the song we've been working with in this lesson, seemingly defies theory. It thumbs it's nose at us soulfully, and sends us theoreticians back to the drawing board in a hurry. Here's what to look for in a blues song:

A7 D7 E7 (Three dominant seventh chords arranged in a I-IV-V manner.)

If we wish to be non-key specific, we could say that if we see a I-IV-V chord progression, and all the chords are dominant seventh chords (A7, D7, etc), we are looking at a blues. By the way, a dominant seventh chord is notated by a letter, followed by a 7 (E7, for example.) A dominant seventh chord is different from a major or minor seventh chord, and therefore Emaj7, Em7, and E7 are three completely different chords. A lot of folks make the mistake of assuming that E7 is Emaj7. It's not, and now you know. Back to business...

The root notes themselves all belong to the key of A Major:

A B C# D E F# G#

We see that A is the I, D is the IV, and E is the V. However, usually, only the V chord (E7, in this case) is a dominant seventh chord. Based strictly off the A Major scale, using only scale tones, we would end up with the following progression:

Amaj7 Dmaj7 E7

As there's only one dominant seventh chord per key, and the blues uses three...At first glance, it looks like the blues progression is in three different keys! To further confuse matters, common practice puts a minor scale (the minor pentatonic) over these chords! What?!

That's the blues sound. The theory can make your head ache, but at the end of the day, it works because we accept it. When we see a series of chords such as the ones outlined above, we would call it a Blues in A. The most popular scale to solo over a I7 IV7 V7 progression is the minor pentatonic scale. However, a major pentatonic scale sounds country or southern rock over the progression. Try it to see for yourself.

(The major pentatonic is the second mode, or shape, of the five pentatonic scales. See Soloing - Part 2 for a diagram. Another way to accomplish this is to drop the familiar minor pentatonic shape down three frets from where you would usually solo. If you're in the key of A, F# minor pentatonic is the relative minor of A major, and hence, the minor pentatonic scale played on the second fret will yield the notes in the A major pentatonic scale.)

A postscript: Key Signatures

Wait a minute! Some of you may have heard about a mysterious concept called a key signature. The key signature of a song is a fast way to figure out what the key is, and it essential for music reading. A very useful thing to know and it will be the focus of the next installment, as it deserves it's own write up. However, a brief explanation would be: The key signature is collection of sharps or flats written at the beginning of a piece of music. Since each major scale as a unique number of sharps or flats, the key signature serves to identify which scale the song is built from. But, in the case of a lot of songs, there's minor shifts in the key, called a tonality change, that the key signature will not reflect. It's important to know how to analyze a progression from the chords themselves. Also, when you're writing a song, you won't have a key signature to look at! Stay tuned, we will cover key signatures in more detail.

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.

32 comments sorted by best / new / date

    Wow1 awesome article! Wish i had this when i started out.. now i jus like figure it out by ear i guess... took me a while to get here though =D
    wow...this whole analyzing chord progressions is giving me headaches... i tried analyzing Here Comes the Sun by T
    JoshUrban wrote: G major, A Dorian, B Phrygian, etc, are all the same thing (share the same key signature.) Try writing out the notes, and you'll see they're all variations of the same scale. G Dorian, G Mixolydian, etc, belong to different keys.
    though they share the same notes, they are not the same thing. you can't play B Dorian over a G major progression, you'll just be playing G major no matter how you think of it. the way you said that can lead to a lot of confusion about what modes are. It's not the same scale starting on a different note, it's a whole different tonality. the intervals are different, the way things resolve is different, and it has a whole different flavor. It's like with relative majors and minors. though they use the same notes, they are two different things, and if you tried to play G major over an E minor progression you would just be playing E minor. So it is incorrect to say they're the same thing.
    "If the key of the song is discovered, in this case, G, then you can use the G major scale and it's related modes to solo over it. In more detail, G Ionian, A Dorian, B Phrygian, C Lydian, D Mixolydian, E Aeolian (Natural minor), and F# Locrian. Keep in mind that this is a very basic view, and certain notes of certain scales won't sound too hot over certain chords. But all of these are in key." This is very wrong. it's the type of stuff that we have to correct in MT all the time.
    G major, A Dorian, B Phrygian, etc, are all the same thing (share the same key signature.) Try writing out the notes, and you'll see they're all variations of the same scale. G Dorian, G Mixolydian, etc, belong to different keys.
    hello guys! i need help. could somebody explain to me how G major scale is related with A Dorian, B Phrygian, C Lydian, D Mixolydian, E Aeolian (Natural minor), and F# Locrian????? why not just play G dorian, G mixolydian, G lydian, etc??? im so confused!!!
    Okay, using the major scale, is the chord progression of I, IV, V, in the key of A minor: Am, Dm, Em? thanks in advance
    Josh Urban truly is a hero in the most suckiest up way of the phrase that can be applied without getting a bit close for comfort! I've been through theory books and i've never found a method of learning that's got a personality writing the material or made it into simple steps; and this series has finally gotten my head around alot of it already! Cheers! And the blog is also excellent, again, thanks =] How many installments are there in total if anyone knows?
    I find it so damn boring learning music theory. I feel like it tries to make sense of music but I prefer to wonder.
    cool been looking for something like this ive managed to learn the theory that had thus far escaped me over night with ur lessons so keep it up also with something like the sort of chords in the maiden song charlotte the harlot were u use chords like 12th fret A and 12th fret D would those chords be just be a 2 note version of a triad were it was root note -> perfect 4th??
    well written as usual, theres something i dont really like though: you need to read all the previous lessons to understand your sick method of thirds which could be good for beginners at first, but makes your lessons impossible to understand for any average skilled guitarist whos not into theory coming here in the middle of your crusade
    Ooh, this guy uses The Real Book too. I suggest it for any guitarists looking for a challenge
    EZLN libertad
    Good, however, you might want to mention in a later article about secondary dominants, and the fact that you can theoretically have more than one 7th chord that fits
    wow these articles have actually been helpful me and ive actually figured out stuff... ill need to look over this one again tho... that was alot to take in.
    I wish I had the patience to pay attention to this stuff LOL..... I just look at the first and last chord of a song, and play notes from a corresponding scale... if it sounds wrong, (which it really never doesn't for the most part) I just throw in a "blue" note from the blues scale or change from major to minor...
    Excellent article. Charlie999 that chord would an inverted D5 powerchord starting at the fifth.
    I'm really glad that someone's decided to take it upon themselves to explain such useful bits of theory to people that he will never meet. Thanks a LOT man! Your articles are awesome!
    aww awesome man, ive been trying to learn about this stuff, thanks bro
    wow...this whole analyzing chord progressions is giving me headaches... i tried analyzing Here Comes the Sun by The Beatles (using this method) and i ended up with three possible keys: D major, E major and A major. I was more leaning to the A major though, because the song ends and finished with that chord, and i looked it up on Google and it turned out to be A major. What confused me though was there were two dominant chords: E7 (could only fit into A major) but there was also B7 (could only fit into E major)so that was really confusing. Ill try to keep applying this method, but its not as straightforward as i thought/hoped it would be... can you please suggest some other easy tunes for analyzing? I cant just grab my favorite songs since a lot of them use power chords and i dont understand how to find key for power chord progressions... Anyway, its a great lesson and it was really helpful. Ill keep studying. Thanks!