Welcome back. In Part 1, we learned how to come up with a diatonic third harmony line to a single-note melody in a minor key. This simple-to-understand-and-execute technique is a staple of rock dual-guitar harmonies. Here’s a quick recap via three short definitions and a simple example:
- Harmony (a quaint definition!): Two notes played at the same time that sound “pleasing.”
- Diatonic: Only using the notes within the scale being used.
- Diatonic Third: The note in the scale being used that is two notes higher than the one you want to harmonize.
Simple Example: If I’m playing in A natural minor (A, B, C, D, E, F, G), and I want to find a “pleasing” sounding diatonic third harmony note that will complement a D note, I merely count up two notes within the scale. The resulting note is F — so that’s the diatonic third for the note D. Easy, right? Cool.
“The Trooper” by Iron Maiden: When 3 Becomes 6
Yeah, I know, the “when 3 becomes 6” has probably got you scratching your head and/or questioning my sanity. Let me explain by referencing specific times within the accompanying video that shows me playing both guitar parts in the intro to this classic Iron Maiden cut. For (alleged) added clarity, I’m using a black Strat with a white pickguard for Dave Murray’s part and a white Jackson Adrian Smith signature axe for his part.
I should also point out that this song is in E minor, and the scale being used in the intro is our good ol’ friend E natural minor (E, F#, G, A, B, C, D). That stated, here goes:
1:13: The song starts with Dave (black Strat) playing the main descending riff while Adrian (white Jackson) plays the diatonic third harmony line — which is the same exact thing except two notes higher in the E natural minor scale — exactly as we learned in Part 1. Nice!
1:17: The repeated dual-guitar harmony melody line begins with the main line on the left of the screen (black Strat) and the harmony line on the right (white Jackson). But wait…
Looking closer at the harmony line on the right, something is definitely fishy here. Yep, this time the harmony line appears to be lower than the main one, not higher! What’s going on? That’s no longer following the “diatonic third formula” we’ve just mastered. Huh?!
Don’t fret, though. All is well — even though the harmony line is indeed lower than the main melody part. Why? Well, this is where the seemingly nonsensical phrase “when 3 becomes 6” kicks in. Read on.
Sixth Sense!
As you’ll see and, equally importantly, hear in the accompanying video, when I play Adrian’s lower harmony line an octave higher, all his harmony notes are now where we’d expect them to be: a diatonic third higher than the notes they’re harmonizing in the main melody! So, for me at least, the easiest way to look at his lower harmony line is to consider it as the diatonic third harmony line to Dave’s main melody but played an octave lower. Make sense?!
As you can also hear, even though Adrian’s line is the lower of the two, Dave’s part remains the main melody. So, that’s a great idea to experiment with, because moving the diatonic third line an octave lower does darken the mood or vibe of the resulting dual-guitar harmony line. And if you wanted to be adventurous, you could even try a mix ‘n’ match!
The next logical question goes something like this: “OK, I get it, but what does ‘6’ have to do with anything?” The answer is simply this: because now the interval between the lowest and highest note is a diatonic (within the scale, remember?) sixth! Let’s hammer that truth home via a quick example:
Let’s say the note in my E natural minor melody that I want to harmonize is G. Using our tried-and-tested diatonic third method, we merely go to the note that’s two notes higher in the E natural minor scale, which is B.
G = the first (duh!)
A = diatonic second
B = diatonic third
Now, if we decide to play that B note an octave lower, let’s see where the G sits relative to the B within the scale (i.e., diatonically, if we want to get technical!) and count…
B = first
C = second
D = third
E = fourth
F# = fifth, and…wait for it…
G = sixth
To misquote Spinal Tap, “none more simple.” And that, my friend, is “when 3 becomes 6.” Figure 1 illustrates these two intervals visually.
Figure 1
Playing Parallel Lines
Next up we’re going to talk about a trio of parallel intervals that are frequently used in rock. Before we do though, I guess I should give the term “interval” its music theory definition. According to “the Googles”:
Interval: In music theory, an interval is the difference in pitch between two notes.
This difference can be described melodically (e.g., minor third, major third, an octave) or in terms of semitones and tones. In case you’re not 100% sure of what a semitone and a tone are, let me quickly explain them both in “guitarist friendly” terms…
Semitone: When two notes on the same string are a fret apart. For example, the C note at the third fret on the A string is a semitone (one fret) higher than the B note at the second fret on the same string.
Tone: When two notes on the same string are two frets (or two semitones, geddit?) apart. For example, the C note at the third fret on the A string is a tone (two frets) lower than the D note at the fifth fret on the same string.
As you’ve no doubt already ascertained, two semitones = one tone.
IMPORTANT NOTE: Sometimes you’ll see the terms “step” and “steps” used. Here’s the relationship between steps, tones, and semitones:
One semitone = half-step
One tone = whole step
Figure 2
Figure 3
So, the 3-fret distance/interval between E and G on the same string could be referred to as follows:
Three semitones or one-and-a-half tones or three half-steps or astep and a half.
Also, as pointed out in Part 1, melodically this interval is called a minor third.
Got it? Good. Let’s move on. Next up is a quick explanation of the trio of parallel intervals we’re gonna be talking about.
Parallel Interval #1: The Octave
Simply put, if we ascend the E natural minor scale, an octave is the distance/interval between the first note, E, and the next E note we play as we climb the scale. This is shown with regards to F# in figure 4.
Figure 4
So, as also shown in figure 4, the interval between the G at the 15th fret on the low E string and the second time we hit G (at the 15th fret on the high E string) as we ascend the scale is two octaves.
In terms of frets, the octave of any note on any string is the one that’s exactly 12 frets higher, assuming you don’t run out of frets of course! That’s why the 12th fret on every guitar is marked with two dots, two blocks, or two somethings!
Figure 5
I should also point out that an octave (or two or three) of any note in any scale is always diatonic (within the scale). Why am I stating what you might well consider obvious? Because that’s not always true of the next two parallel intervals we’re gonna discuss: the fifth and fourth.
NERDY NOTE: In terms of frequency, an octave is the interval between one musical note and another that has double its frequency. For example, the frequency of the open G string note is 196Hz, and the frequency of its octave note at the 12th fret on the same string is 392Hz…and 196 x 2 = 392. Now you know — hoorah!
Parallel Interval #2: The Parallel Fifth
The parallel fifth of any note is the note that’s three-and-a-half steps, or tones, higher. Or, once again, if you find that thinking in terms of frets is easier: the parallel fifth of a note on any string is the note that’s seven frets higher on the same string.
For example, the parallel fifth to the G note at the third fret on the low E string is the D note at the 10th fret on the same string. An easier way to find the parallel fifth of any note on the low E string is this: go to the note two frets higher on the A string. So, the parallel fifth of our G at the third fret on the low E string is the D at the fifth fret on the A string. This is shown in figure 6 — an image that you should be extremely familiar with!
Figure 6
Yep, figure 6 is the good ol’ root/fifth power chord we know, love, and (ab)use!
Now I know what you might well be thinking: “If we’re still thinking E natural minor, then D is in that scale, so isn’t this interval diatonic?” The answer is “yes,” but it’s not true of every note in the scale. Most parallel fifths are diatonic, but one isn’t. To clarify, check out figure 7 below.
Figure 7
| E Natural Minor Note | Parallel Fifth Note |
| E | B |
| F# | C# |
| G | D |
| A | E |
| B | F# |
| C | G |
| D | A |
As indicated by the bolded C# — not all the parallel fifth notes are diatonic, hence the use of the word “parallel.”
NOTE: Due to the way the guitar is tuned, the “one string over, two frets up” method of finding the parallel fifth note of any note on the low E string is also true of all notes on the A, D, and B strings. The method for the G string? One string over (B) and three frets up…due to the tuning of that pesky B string.
Parallel Interval #3: The Parallel Fourth
The parallel fourth of any note is the note that’s two-and-a-half steps, or tones, higher. Or, yet again, if you find thinking in terms of frets easier: the parallel fourth of a note on any string is the note that’s five frets higher on the same string.
For example, the parallel fourth to the A note at the fifth fret on the low E string is the D note at the 10th fret on the same string. An easier way to find the parallel fourth of any note on the low E string is this: go to the note at the exact same fret on the A string. So, the parallel fourth of our A at the fifth fret on the low E string is the D at the fifth fret on the A string — simple stuff.
NOTE: Due to the way the guitar is tuned, the “same fret, one string over” method of finding the parallel fourth note of any note on the low E string is also true of all notes on the A, D, and B strings. The method for the G string? One string over (B) and one fret up.
As was the case with the parallel fifth, some parallel fourth notes in any given scale are diatonic (within it), and some aren’t. Here’s another chart to illustrate this truth, and this time we’ll go with A natural minor.
Figure 8
| A Natural Minor Note | Parallel Fourth Note |
| A | D |
| B | E |
| C | F |
| D | G |
| E | A |
| F | Bb |
| G | C |
Once again, there’s a single, non-diatonic, rogue note: Bb.
The Separation of Church and Rock!
As mentioned in the accompanying video, when researching this piece, I came across an article about vocal harmonies, and the author included a section titled: “Avoid parallel fifths, fourths, and octaves.” In it, he stated that parallel octaves are “weak,” and that parallel fifths are “weak” yet “ominous.” He also (correctly) pointed out that the fourth is merely an inverted fifth, before declaring that “parallel fourths are also to be avoided.”
Now, while his “avoid these” stance might well be true for a choir, it is certainly not true for rock — be it classic, alternative, or metal. All three intervals are (ab)used a lot! The parallel fifth, as already stated, is the rock staple that is the power chord; the parallel fourth is an inverted power chord. And you can’t tell me that timeless riffs such as “Smoke on the Water” are “weak”! I rest my case #1….
Kiss and Tell
At 9:48 on the video, I illustrate how the members in KISS cleverly use two guitars and a bass, plus parallel fifths, parallel fourths, and octaves to wonderful effect in the intro to “Detroit Rock City” — a true hard rock classic. I rest my case #2…
Slaying with Parallel Fourths and Octaves
At 11:04 on the video, I demonstrate how the almighty Slayer combines parallel fourths and octaves to create hauntingly ominous, dual-guitar parts in songs such as “Mandatory Suicide.” Case closed!
Figure 9 shows the dual harmony line I play to illustrate the clever way that Messrs. Hanneman and King shared their duties on the aforementioned song: the guitar that plays the lower three parallel fourth notes plays the upper notes of the two octaves that follow and vice versa. Simple but brilliant IMHO.
Figure 9
Conclusion, Sign-off, and “What’s Next?”
Hopefully this article and video pairing has proved to be a useful and easy-to-understand introduction to the world of inverting diatonic thirds to create diatonic sixths à la Iron Maiden and then parallel fourths, fifths, and octaves like KISS and Slayer do so well. There’s still more to explore though, and we’ll get to that in Part 3, which will follow shortly.
Until then, take what you’ve learned and come up with some dual-guitar harmony ideas of your own. And you don’t need a looping pedal or a fancy, high-tech recording device either. As long as your phone can record, just tap your foot, play the line you want to harmonize, and then experiment over the playback.
Thanks for reading and watching. Until next time, I hope you have fun with these dual-guitar ideas.