one of my target goals last year was to start writing an original song. i spent a fair bit of time checking out different chord progressions, but wasn't sure how to modify them to make them "unique" (if there is such a thing). a big thank you to @Jim Mrvos for recommending "the berklee book of jazz harmony" by joe mulholland and tom hojnacki. using a few basic techniques in the book, i modified a I IV V I progression into something with a lot more character.

if you've taken the music theory course on this site ( https://www.guitarfam.com/challenge-page/music-theory-guidebook ) then you should be able to follow the steps i took.

i'm not going to explain why this works here, just simply what i did because you don't need to know how an engine works to drive a car.

i'm going to start with a 1-IV-V-I progression in the key of C major...

it sounds like...

it is worth noting here that the chords serve specific functions. the I chord is the tonic... it is the root of the progression, often first and last chord in a song. the IV chord is the subdominant. it is unstable and wants to resolve back to the tonic. the dominant is the most unstable, and want to resolve back to the tonic even more than the subdominant. when we substitute chords, it is important to know the function they are serving.

the first substitution is to modify the I IV V I to a Imaj7 IVmaj7 V7 Imaj7. remember in the major key, the I, IV and V chords are major. the I and IV chords are both major 7th, while the V chord has a minor 7th, making it a dominant 7th, which is why we use V7 instead of Vmaj7.

so now we have:

which sounds like:

note that if we were writing a blues song we would probably use all dominant 7ths instead of major 7ths. we're jazzing this up a bit.

next, we're gonna add some chords from within the C major scale. these are called diatonic chords... we'll start with the I chord, our tonic. there a few substitutions for a I chord, including I maj7, vi7, and iii7. of these, the iii7 is the weakest, and we'll use it for a different purpose later. the vi7 however, is a pretty good substitute, so we'll extend the time the song spends in the tonic function by adding a measure of vi7 after our Imaj7.

next, lets find a good alternate for the subdominant IV chord. turns out that a ii7 works well. so well, in fact, that a core staple of jazz is the ii V I progression. so we'll add a ii7 after the IV maj7.

we now have Imaj7 vi7 IVmaj7 ii7 V7 Imaj7...

listen to how much the I and vi sound alike. also listen to how similar the IV and ii are.

we're nearly there...

next we're going to add some chords to separate the ones that sound too much alike... let's start with the progression from Imaj7 to vi7. we need something in between to lead into the vi7 (Am7). just like the dominant 5th wants to resolve to a tonic, a dominant fifth of a chord wants to resolve to that chord. let's add one of those. what is the 5th in Am? A-C-E... so E. thus the V7 of Am is E7. we'll add that after the I maj7 (Cmaj7).

using the dominant 5th of a chord other than the tonic is known as a secondary dominant. the root of the chord will always be in key, however other notes in the chord may be outside of it.

for example, note that the V7/vi is E7, also written III7. in the key of C, the iii7 chord should be minor (EGBD). the G# in the E7 is outside of the C major scale. this is essentially the same topic we discussed in the analysis of "on the road again".

let's look at the end... i like to end on a C instead of a Cmaj7. the V7/I is just the V7, or G7, which precedes it. note that we showed earlier that the ii7 V7 I progression is staple of jazz. so we have a Dm7 in front of the G7. what if we wanted to use the secondary dominant of G7 instead? what would that be? G-B-D, so D. thus the V7/V7, the V7 of G, would be D7. so you see that either D7 or Dm7 would work here,

thus when you use a secondary dominant to approach a chord, you can use either a secondary dominant of the secondary dominant or the relative ii chord. so for G, we can use either the V7 of G, D7, or the relative ii of G, Dm7. we can keep expanding this pattern.

keeping the Dm7 G7 C progression, we can lead the Dm7 with it's secondary dominant, the V7/ii. for the Dm chord, DFA, the A is the 5th. thus, we can introduce the Dm7 by placing the A7 in front of it. and let's then take the relative ii of A7. the 5th in ACE is E, thus we could use E7 as a secondary dominant (just like we did for Am7) or we could use Em7 as a relative ii. we'll use that.

note that Em7 is also the iii7, which is a diatonic chord (all notes in the key defined by our tonic, C). this means it will serve dual functions. when we first hear it, it will sound like a partial resolution from the preceding IV7 chord, but then the progression to A7 will cause it to take on the role of the relative ii of A7.

all that spelling out chords getting to be too much? use the circle of 5ths. if you want to lead into a chord, find the root of the chord on the circle, and create a dominant 7 chord whose root is one note clockwise on the circle of 5ths. want to lead that note too? move clockwise on the circle one more time. as the previous chord is already a V7 of a chord, we can either use a dominant 7 chord (V7) to lead it, or a minor 7 (relative ii7) chord. the root of the chord will be the same in either case. thus, if you look at the circle of 5ths you can see that if you want to lead an Ab chord, you would add an Eb7 in front of it (one slot clockwise for a V7). you could lead the Eb7 a Bb7 (one slot clockwise to make a dominant 7th, for a V7/V7) or a Bbm7 (one slot clockwise, make a minor 7th, or relative ii of V7).

so our progression now is a I III7 vi7 IVmaj7 iii7 VI7 ii7 V7 I (Cmaj7 E7 Am7 Fmaj7 Em7 A7 Dm7 C)

you can hear this moody progression is a far cry from where we started.

there's just one last thing. i took the progression and added a very simple half note melody on top of it. often the melody is simply adding or removing the 7th or leading into the next root. i limited the high e string to keep it from hiding the melody. i also restricted the bass notes, using root notes in the bass for I and V chords, but using inversions elsewhere to keep the bass line reasonable and not jumping all over the place. in one instance, the E7, i removed both E notes, thus the second measure chord is missing its root, and technically would be a G#dim. I left it labeled as E7 to identify it's function.

and here is the final progression...

which sounds like...

my next steps from here are to apply these and additional concepts, like subV and cadence to a more complicated progression, and will probably modify a 12 bar blues progression. i'll also be working on learning the minor harmonization techniques, particularly some of the dorian progressions.

as much as anything else, for me this has been an adventure into creating scores in tuxguitar.

hopefully you've seen how using a few techniques to modify progressions can allow you to significantly alter the sound of the progression in a predictable way.

i hope that maybe someone out there who finds music theory too boring will see how easy it is to get some practical use even without understanding all the details behind it.