As a guitar player, you may have come across the expression "2-5-1" before. If you're coming from a Jazz, or perhaps even Blues background, this phrase might sound familiar. If, however, you come from a more Rock oriented musical upbringing, this term might sound mysterious or confusing. This article should hopefully give you a decent understanding of what "2-5-1" means and how to incorporate it in your playing.
Before we tackle the "2-5-1" head on, we need to establish a few basic concepts. The first deals with how chords are constructed.
Harmonising the Major Scale
We're going to work in C major for this lesson, but these concepts apply to any key. Let's start with a simple major scale, just 1 octave.
As you can see, we've just got all the notes of the scale from low to high. To "harmonise" these notes and create chords, we need to add extra notes to them. For "triadic" harmony, we're going to add thirds to each note. In this case, we skip a note and add the next one. Over the C we add an E, the D an F, the E a G and so on.
We can add another third on top of that to create a full 3 note chord. These chords are called triads, as they contain three notes and are the most commonly used type of chord.
We can keep extending these chords by adding more thirds on top, but for now, we're just going to add one more set of thirds to create a set of 4 note chords.
Now we have seven chords,
C major 7, D minor 7, E minor 7, F major 7, G dominant 7, A minor 7 and B minor 7 flat 5.
To make life easier, chords are commonly referred to by their numerical placement in the scale. For example, instead of having to say "E minor 7" you could just refer to it as the "3 chord" or to be specific to a key, the "3 of C major". Because numbers get thrown around A LOT in music theory (thirds, third degree, triads etc.) the chords are labeled with Roman Numerals, to distinguish them.
Instead of chords 1, 2, 3, 4, 5, 6 and 7, we have chords; I, II, III, IV, V, VI, VII
Tension and Resolution
The next step to understanding the 2-5-1 (or II-V-I) is to make sure we understand what is meant by "tension and resolution". To create harmonic development in modern music, we need to take listeners on a musical journey. To do this, we need to set up natural movement in our chord progressions. If we have a particularly tense, or "unfinished" chord, the listener will subconsciously (or consciously) want it to be "resolved". This basically means that we follow up the tense chord, with a chord that settles all the tense intervals. In diatonic major harmony (which is what we looked at above) the easiest was to create tension is with the V chord, in this case, the G dominant 7.
To resolve this chord, we simply follow it up with the I chord, the C major 7.
When a V chord moves to a I chord, the 3rd and 7th interval of the V resolve to the Root and 3rd interval of the I. These two instances of semi-tone (one fret) movement, make the chords perfectly suited to be played one after another.
This movement, the V chord to the I chord, is commonly preceded by a "set up" chord. In 99% of cases, and in hundreds of classic examples, this chord is the II chord.
This is where the expression II-V-I comes from. It simply refers to the chord progression: II chord, V chord, I chord. In this key, that would be:
D minor 7, G dominant 7 and C major 7.
In the key of E it would be:
F# minor 7, B dominant 7 and E major 7
In the key of Bb it would be:
C minor 7, F dominant 7, Bb major 7
Etc.
Taking it Further…
You can get a lot of mileage out of a straight, unaltered or extended II-V-I, but there is plenty we can do to take it even further. As I mentioned before, if we keep stacking thirds on top of each chord we get richer sounding, more involved harmonies. After the 7th comes the 9th, then the 11th and finally the 13th. If we apply these to each chord in a II-V-I then the tension and release is amplified even more. Let's take the previous three examples and beef them up a little.
In the key of C:
In the key of E:
In the key of Bb:
At the moment, these II-V-I progressions are very linear. They begin, set up tension, and resolve, adding the sense of finality to the progression. With one simple addition, we can make this progression circular, meaning it can continue moving in a loop. Continuing from the logic above, that the dominant 7 chord (the V chord) wants to resolve a 5th below, we can use another dominant 7 chord to bring us back to the II chord. After we play the I chord, we introduce the VI chord. In diatonic harmony, this chord would be a minor chord, a 6th above the key centre, but in this case we are altering it to become a dominant 7 chord.
This change has turned the II-V-I into a II-V-I-VI, a progression commonly known as the "Rhythm Changes". The name for this progression comes from George Gershwin's jazz standard "I got Rhythm", the main section of which is a repeated I-VI-II-V (just a II-V-I-VI from a different perspective). Because of the circular nature of this chord progression, it became a popular practice point for jazz musicians, who can use this loop to practice improvisation or reharmonisation techniques. We can still add all the same extensions we looked at above when playing through this progression, but we need to be a bit careful on the VI chord. Because it is technically outside the key centre (because we've changed it from a minor to a dominant chord) we can't necessarily use all the normal extensions. What we can do, is change this into an "altered" dominant chord. An "altered dominant" is simply any dominant 7th chord, with an added b2 (b9), #2 (#9), b5, #5 or any combination of these altered tones. This creates an extremely tense sound that begs to be resolved to the II chord. Here are our three examples again, but with an added VI chord, played a few times around. Just see how this simple chord progression, with a few extensions, can sound really interesting.
In the key of C:
In the key of E:
In the key of Bb:
The tritone substitution
If we want to take this even further, we can interest the concept of chord substitution to the mix. This topic contains enough potential to fill a thousand pages, but for now we'll stick to the most common type of substitution, the tritone substitution. A tritone is a rather delicious name for a b5 (or #4) interval. To locate these on the guitar, we simply play a power chord, and lower the top note.
Whenever we encounter a dominant 7 chord, we can substitute it for another dominant 7 chord, a tritone away. For example, if we are met with a C7, we can switch it for an Gb7
This works, because the 3rd and 7th from the original dominant, are always present in the substitution. Even though the chords are wildly spaced apart, they still have enough harmonic similarities to be interchanged in a progression. Extensions on these substituted chords, like the VI chord, can be tricky, so it is recommended to start off with just a straight dominant 7, introducing more elaborate tones as you get familiar with the theory. Here's a short example of a simple I-VI-II-V progression straight, and then with substitutions.
It might seem a little bit arbitrary for this progression to have such a wealth of study behind it, but if you ever start looking at jazz standards, you will find that many of them (many many many!) feature a movement of II-V-I at some point. It is a jazz musicians bread and butter, and a fantastic progression to practice improvising around. In just 3 chords, we are able to include a set up, tension and release. Try working out some II-V-Is in different keys, or analysing some of your favourite songs. You will be surprised at how often this progression occurs. In the second part of this article, we will be tackling the challenge of improvising over these progressions.
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