Here we’re going to walk that out in a practical way by studying some of the most basic intervals, using them to develop tetrachords and applying them in a practical way to improve our improvising on the guitar. We can think of intervals and tetrachords as our topic and melodic guitar solos as our or application.
Explaining Intervals and Tetrachords
If you don’t know what intervals or tetrachords are, think of them as the most basic building blocks of melody, or in our case, guitar solos.Since a tetrachord is just a collection of intervals (in a major key), let’s first explain what an interval is.
In music, an interval is simply the space between two notes, or two frets on the guitar. For example, a whole step up or down on the guitar is when you move two frets; say from the third to the fifth. That’s an interval that we call a major second. Moving a half step or one fret is called a minor second.
There are other intervals that you can look into if your curiosity gets the best of you, but for this lesson and for the purpose of defining tetrachords, we only need to know about major and minor second intervals, as well as the major third, which we’ll touch on later.
Major Second (whole tone)
E|——–
B|——–
G|——–
D|–3–5–
A|——–
E|——–
Minor Second (half tone)
E|——–
B|——–
G|——–
D|–3–4–
A|——–
E|——–
Now, back to tetrachords. You get a tetrachord in modern music with any four-note segment of a scale. So in a major scale a tetrachord consistents of two whole tones, followed by one semitone; whole, whole half.
In a tab:
E|————–
B|————–
G|————–
D|–3–5–7–8–
A|————–
E|————–
Tetrachords and the Major Scale
Now that you know how to get from intervals to a tetrachord, let’s look at how tetrachords fit into the broader scope of a major scale. If you put two tetrachords side by side, with one whole tone between them, you get the basic sequence of intervals in a major scale.
So for example, the following tab would be considered a major scale (or diatonic scale) since it follows the required sequence of intervals between notes.
E|————————–
B|————————–
G|————————–
D|————————–
A|————————–
E|–3–5–6–8–10–12–13–
Applying Knowledge of Tetrachords to Help you Improvise
So how does this help us? Well first, it provides some easy-to-remember structure with which to improvise. Let’s say you’re playing along with a G chord or in the key of G major. You want to add a fill but don’t know where to start. Well, let’s examine our options.
If we just stick with G, we’ve got several choices.
E|–3–|———(3)——
B|–3–|————-(8)–
G|–0–|——(0)———
D|–x–|–(5)————-
A|–2–|——————
E|–3–|——————
We first see the G chord which is then followed by four notes, all of which are also G. All we have to do is pick one and apply our major tetrachord pattern.
Let’s go with the note on the third string at the fifth fret.
E|–3–|—————–
B|–3–|—————–
G|–0–|—————–
D|–x–|–(5)–7–9–10–
A|–2–|—————–
E|–3–|—————–
All we’ve done is added two whole tones and one semitone to our G note and chord. But it’s not terribly interesting, so let’s add one more whole tone to get us to the 12th fret and mix things up a bit with our other notes by adding some technique.
E|–3————————————-
B|–3————————————-
G|–0————————————-
D|—–5–/9–7–10–9b10–9–7–/12–5~–
A|–2————————————-
E|–3————————————-
Now that we’ve mixed the notes up, added some slides, a bend and a little vibrato, we’ve got a unique sounding melody in the key of G major that works with our chord. If you wanted a minor sound, you could just experiment by mixing up the order of the intervals.
Using a Chord’s Root Note
One thing you can always do is start your improvising at the root note of whatever chord you’re playing or whatever key you are playing in.
For example, if a song is in the key of E, then you can start your improvising at any of the following notes.
E|———–12——–
B|—————5—–
G|——–9————
D|——————2–
A|—–7—————
E|–0——————
Each note in the tab is an E. So if you remember the sequence of intervals for the major scale (whole, whole, semi, whole, whole, whole, semi) you can use that sequence to build a melody off any of these notes.
Identifying the Major Third and Using Other Strings
You might have noticed that the entire line of the tab we came up with earlier occurred on one string. That’s not necessarily a bad thing, but it’s also not an entirely functional way to play the pattern. An easier way to construct the sequence is to use other strings. To do that, we need to identify another interval.
Notice that we traveled from the fifth string all the way up to the ninth.
E|–3–|—————–
B|–3–|—————–
G|–0–|—————–
D|–x–|–(5)–7–9–10–
A|–2–|—————–
E|–3–|—————–
That jump is another interval that we call a major third.
What’s helpful about a major third is that we can play the same interval like this:
E|——–
B|——–
G|—–4–
D|–5—–
A|——–
E|——–
It’s exactly the same, which means we could play our original tab like this:
E|–3–|—————–
B|–3–|—————–
G|–0–|———-4–5—
D|–x–|–(5)–7———
A|–2–|—————–
E|–3–|—————–
The interval sequence is still whole tone, whole tone, semitone.
Stringing Intervals and Note Sequences Together
If you keep following this pattern in a major key, you can string together any number of notes all the way up and down the fretboard. All you need to do is stick to the tetrachord interval sequence. Assuming you’re playing in a major key, this is something you can always use.
Experiment with different combinations and try to memorize longer sequences that you find yourself using more often. Certain players will tend towards different note combinations, so if you find a line of notes that you keep going back to, take the time to memorize and use it to expand your command of the fretboard.
The more you understand why you’re playing what you play and the purpose of each note, the easier it will be for you to improvise because improvising isn’t just guessing and getting lucky. It’s a variation on a theme or variety within structure. Know the structure and you’ll become a far better improviser on the guitar.
