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Music Theory - Identifying Intervals

Published May 20th, 2007. © Chris Juergensen/chrisjuergensen.com. All Rights Reserved.


I've gotten a few e-mails asking specifically about theory. Most of the lessons in "The Infinite Guitar" and on the chrisjuergensen.com site start around the middle and a basic understanding of music theory is a necessity to make good use of them. Intervals are the building blocks of music and I've decided to dedicate this lesson to identifying them. Writing it took me back to my college days in Theory I class. If you don't have any experience dealing with theory it might seem like a big step but take my word for it, if you take a little time and work on it, most of the things that confuse you, will go away. I've written out some exercises for you to do in this lesson, but they are most likely too short for it to turn into a real workout. I would suggest that you write out several pages of similar examples and work on them everyday until identifying intervals becomes second nature. This is the question that started the whole thing:

Q: Why is the IV chord harmonized to a major 7th chord while the V chord is harmonized to a dominant 7th chord?

A: Lets first make sure that we understand what we are doing when we harmonize a scale. When we harmonize 7th chords from the major scale, we are simply stacking notes a third apart to make them:

If we do it for every note in the scale we will get the following seven chords:

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Let's assume you have this harmonization concept down. The confusion is in why these chords are what they are. Why are the IV and V chords different? For that matter, why aren't all the chords the same? I have to be very careful not to confuse you here so I'll take my time. You see, it is all about the intervals that make the chords what they are. An interval, as the word suggests, means the distance between any two notes.

To understand the makings of music you must be able to identify all the intervals, and know the proper combinations of the intervals in which chords are constructed. It is safe to say, intervals are the very essence of harmony. How many intervals are there? There are basically six intervals, one for each note from the root of the major scale: 2nds, 3rds, 4ths, 5ths, 6ths and 7ths. These intervals however come in different qualities. What I mean by this is that intervals of 2nds, 3rds, 6ths and 7ths can be major, minor (and sometimes, but not very often diminished and augmented). 4ths and 5ths can be perfect, diminished and augmented. Before we go on to the actual combinations of these intervals to build chords we first must be able to identify each interval.

How can we identify them? There are several methods and to be able to identify intervals through each of these methods is the ultimate goal. When I went to college and took music theory, the first theory class (there was Theory I - IV) is mostly identifying chords through first identifying the intervals contained within. I remember that my best friend at school and I both could identify the intervals, though through different methods. I simply memorized the intervals by name, in other words, I just knew that an interval of C-E was a major 3rd, and therefore an interval of a C-Eb was a minor 3rd. I memorized them like we memorize our times tables in the third grade. My friend Kevin visualized the two notes on the fretboard of his bass, and recognized the shape as a major third. You could also possibly identify the intervals by the sound they make. For example, you might imagine the sound of a C and E note played together and recognize the interval, It would, by the way sound like the first two notes in "Oh When The Saints Go Marching In."

It is in your best interest to understand the major scale and be able to write them all out. Without this skill, music is difficult to understand on a theoretic basis anyway. If you can't write out the major scale yet, bookmark this page, get out some staff paper and get to it. I don't have any lessons on the site on how to remember and write out key signatures and major scales, so you will have to figure it out yourself. If enough people bug me to write one, I may do it for you, but for now get out some staff paper and practice writing them out.

Let's work on the intervals. I'm going to take a double attack method with you on this one. We are going to identify intervals through both fretboard visualization and simple memorization.


As I mentioned, there are six basic intervals: 2nds, 3rds, 4ths, 5ths, 6ths and 7ths (although octaves are considered intervals as well). First I want you to simply identify what the interval is. I don't care what the quality is yet, in other words you don't need to tell me if it is major, minor, perfect, diminished or augmented, just that it is a 2nd, 3rd, 4th, 5th, 6th or 7th. Just count from the bottom note. Our first example is a C and E note. Count from C up to E, C is 1, D would be 2 and E is three. The interval is a 3rd. Write in the interval under each example.

Ex.1

Although there are seven intervals, there are basically five qualities of intervals: major, minor, perfect, augmented and diminished. I will use a type of shorthand from now on: major will be notated as: M, minor as m and perfect as P. Diminished and Augmented intervals will also come into play and they will be notated as D and A. So a major 3rd will be written like this: M3 and a diminished 5th like this: D5.

Major/minor intervals - 2nds, 3rds, 6ths and 7ths are for the most part major or minor. If you raise a major interval by a half step it becomes augmented. If you lower a major interval by a half step it becomes minor. A minor interval lowered by a half step becomes diminished. Try to memorize the chart below:

2nds, 3rds, 6ths, 7ths
A
M
m
D

Augmented and diminished 2nds, 3rds, 6ths are pretty rare but diminished 7ths show up in diminished 7th chords. There is no such thing as a perfect 2nd, 3rd, 6th or 7th.

Perfect intervals - 4ths and 5ths can be perfect, augmented or diminished. A perfect interval raised a half step becomes augmented while a perfect interval lowered a half step becomes diminished. Again, try to memorize the chart:

4ths, 5ths
A
P
D

Identifying 3rds

Next let's start with identifying 3rds. First let's identify them without any accidentals (sharps or flats). I'll give them to you in name and quality.

C-E = M3
D-F = m3
E-G = m3
F-A = M3
G-B = M3
A-C = m3
B-D = m3

While you are at it, this is what a major 3rd and minor 3rd interval looks like on your fretboard:

M3
m3

Now I'm going to give you some time to practice identifying the 3rds. Simply write underneath each interval either M3 or m3.

Ex.2


A minor interval made larger by a half step becomes major. A major interval made smaller by a half step becomes minor. Hold your thumb and index finger up like you are showing someone how big something is. Now imagine it as the interval in our first example below before I put a sharp in front of the C note. You should be imagining your thumb as an A note and your index finger as a C note. This interval is an interval of a m3 (you should know this because you memorized it in the last section). Raise your index finger up a centimeter while leaving your thumb alone, this is what happens when we sharp the C note and make it a C# note. The m3 has just become an M3. Are you getting my point? It is about the distance between the two notes. Hold your fingers up again and imagine the same m3 (A-C), if you lower the bottom note (your thumb) a half step, the space between your thumb and index finger gets bigger by a half step (Ab-C). Therefore, the m3 is once again becoming a M3, only this time by lowering the bottom note rather than raising the top note.

Ex.3


Identifying 5ths

Now for 5ths. There are no major or minor intervals here. Easy to remember because other than the last 5th B-F which is diminished, all the other ones are perfect:

This is what a perfect 5th and diminished 5th interval look like on your fretboard:

P5
D5


A perfect interval made larger by a half step becomes augmented. Easy to understand because the interval is getting bigger. Think of a breast augmentation operation. A perfect interval made smaller by a half step becomes diminished. Also easy to understand, diminished means getting smaller. Hold your thumb and index finger up again. Now imagine the first interval below without the flat in front of the D note. Without the flat, it is an interval of a perfect 5th. Lower your index finger a centimeter while leaving your thumb alone. The P5 has just become an D5. Are you seeing it? It is about the distance between the two notes. Hold your fingers up again and imagine the same P5, if you lower the bottom note (your thumb) a half step, the space between your thumb and index finger gets bigger by a half step. Therefore, the P5 is now becoming a A5, this time we lowered the bottom note making the perfect 5th interval larger by a half step. See if you can figure out all the 5ths below.

Ex.4


Identifying 7ths

No perfect intervals here, only major and minor. 7ths:

This is what a major 7th and minor 7th interval look like on your fretboard:

M7
m7

Let's see if you can identify the 7ths below.

Ex.5


I've mixed up the intervals for you in our next exercise.

Ex.6


Identifying Chords

Now the fun begins. If you can identify 3rds, 5ths and 7ths, you can also identify triads and 7th chords. Let's start with triads. The rules are as follows:

Triads
P5
P5
D5
A5
M3
m3
m3
3
1
1
1
1
maj
min
dim
aug

Write the name of the triad below each example (it may help if you write the intervals next to each note).

Ex.7

Now for the 7th chords. Rules are as follows:

7th Chords
M7
M7
M7
m7
m7
M7
m7
m7
m7
D7
P5
A5
D5
P5
D5
M5
P5
A5
D5
D5
M3
M3
M3
m3
m3
m3
M3
M3
M3
m3
1
1
1
1
1
1
1
1
1
1
maj7
maj7#5
maj7b5
min7
min7b5
min/maj7
7
7#5
7b5
dim7

Write the name of the 7th chord below each example.

Ex.8


Voicings and Inversions - You have to keep in mind however, chords are generally not played (therefore written) stacked in thirds, and the order could be anything. In order to find out what the chord is, you will have to mentally stack the notes in thirds to find out what it is. I remember in college, I used to actually write each chord out in thirds on a separate piece of paper in order to figure out what it was. After a while it becomes second nature but at first you may have to do it the same way. Below I took a randomly voiced chord and stacked it in thirds to better analyze it:

Understand what I did? I moved the G note on the bottom to the top so that the chord would line up in 3rds. Once it lined up, it is easy to figure out what it is.

Let's practice rearranging the intervals in to thirds so we can identify the chords better. Stack the notes in thirds on a separate piece of paper if necessary and write the triad name under each example. I did the first one for you. I simply moved the C note on top an octave down and the intervals line up in thirds and I analyzed the chord as an Amin chord. Try the rest yourself.

Ex.9

And the same with 7th chords.

Ex.10


Now that you can analyze 7ths chords, you will finally be able to understand why the diatonic chords are all different. Write the intervalic analysis below each chord and the name above.

Ex.11


Get out your staff paper and start practicing writing out different chords using the charts above. I'll start working on a lesson dealing with the other intervals (2nds, 4ths and 6ths). When you get those down, you'll be able to identify every chord known to man.

Answers:

Ex.1 3 5 2 6 3 7 4 3 6 2 4 7
Ex.2 m3 m3 m3 M3 M3 M3 m3 M3 M3 M3 m3 m3
Ex.3 M3 M3 M3 m3 m3 m3 M3 M3 m3 m3 M3 m3
Ex.4 D5 A5 A5 P5 D5 P5 D5 A5 D5 A5 P5 P5
Ex.5 m7 M7 M7 M7 m7 M7 M7 m7 m7 m7 m7 M7
Ex.6 m7 A5 A3* M7 M3 M3 m7 A5 M7 P5 M3 A5
Ex.7 Fdim Caug Gmin Gaug Adim Daug Bmin C#min Fmin Bb Dmin Edim
Ex.8 C7 Gmaj7 E7 Fmin7 D7 Amaj7 Bbmaj7 Ddim7 F7 Amin7 Dmin/maj7 G7
Ex.9 Amin G F Bmin Cmin D E A Fmin E Cmin Edim
Ex.10 G7 Amin7 Fmaj7 Emin7 Emaj7 Fmin7 Amaj7 D7 Gmaj7 C7 Fmin/maj7 Gmaj7
Ex.11 Cmaj7 Dmin7 Emin7 Fmaj7 G7 Amin7 Bmin7b5

* Although this interval sounds and looks like a perfect 4th the fact that it is written as a Gb-B rather then F#-B makes it intervalically a 3rd, in this case augmented.

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