Ari’s Music Theory Primer

A detailed discussion of music theory is outside the scope of this blog, but here’s my take on some fundamental music theory concepts, so you know what I’m talking about.

Harmonic Theory

In Western music, an octave is divided into 12 equal steps.  Each step is called semitones or half-step.  An interval is a distance between any two notes.

You take all or subsets of those 12 steps, or rather, notes, and form a scale.  A chord is harmony created from two or more notes.

chromatic scale or line is a movement in semitones.  A major or minor scale is made up of 7 notes selected from the 12 notes in a chromatic scale.  A key is a tonal center of any given scale/harmony, also used as an identifier of any scales.  When you choose the 7 notes (actually we think of them as a set of 8, which includes the octave) we follow a certain pattern based on what kind of scale we’re using.

If it’s a major scale, here are the intervals we use to determine our notes.  2-2-1-2-2-2-1.  That’s a series of intervals from the root of the scale, the home note of that key.  If it’s a minor, then the intervals are: 2-1-2-2-2-1-2.

Let’s take C Major, which means its home note is C and it’s a major scale.  The notes contained are C-D-E-F-G-A-B-(C).  Between all those notes are two-semitone intervals, except from E to F and B to C, which are one-semitone interval.  In Western music somebody decided that that’s the default key of all music (I don’t know why that happens to be assigned C).  If you create a scale in other keys, you end up adding sharps (1 semitone higher) and flats (1 semitone lower) to make the notes fit that interval scheme.  For example, an A Major is A-B-C#-D-E-F#-G#-(A).  C is raised to create a two-semitone interval from B, and F# from E.  Raising G to G# satisfies the requirement of making it two semitones higher than F# and one semitone away from A.  Because Western music mostly uses Major and Minor scales, the two-semitone intervals are called a whole-step.  A G minor scale is G-A-Bb-C-D-Eb-F-(G).

triad is a chord made up of three notes.  It typically features notes that skip a note in the scale, such as a C chord in the key of C being C-E-G.  It’s a major triad if the first interval in that chord has 4 semitones and the second has 3.  It’s a minor chord if it’s reversed, with the first being 3 semitones and the second being 4.  There are other kinds of chords but in popular music the vast majority of chords are either major or minor triads, so instead of calling them triads we simply called them chords.

So, you make triads based on notes in your key, and the scale determines whether it turns into a major or minor chord.  And the way I learned to symbolize these chords is by assigning a uppercase Roman numeral to major chords and lowercase to minor chords, with the number indicating which note in the scale is used.  If you’re using the note-name alphabets to describe chords, then alphabets get upper-cased and small “m” attached to minor chords.

Common major scales and their chords:

Key/Root I ii iii IV V vi vii°5
A A Bm Cm D E F#m G#mb5
C C Dm Em F G Am Bmb5
D D Em F#m G A Bm C#mb5
E E F#m G#m A B C#m D#mb5
F F Gm Am Bb C Dm Emb5
G G Am Bm C D Em F#mb5

(I realize the vii chord looks weird — I listed it for completeness sake but don’t worry about it for now — most songs in folk/pop/rock genre don’t use it)

Here are common minor keys:

Key/Root I ii°5 III iv v/V VI VII
Am Am Bmb5 C Dm Em/E F G
Bm Bm C#mb5 D Em F#m/F# G A
Cm Cm Dmb5 Eb Fm Gm/G Ab Bb
Dm Dm Emb5 F Gm Am/A Bb C
Em Em F#mb5 G Am Bm/B C D
Fm Fm Gmb5 Ab Bb Cm/C Db Eb
F#m F#m G#mb5 A Bm C#m/C# D E
Gm Gm Amb5 Bb C Dm/D Eb F

The minor key needs a bit more explanation.  The diminished ii°5 chord is seldom used.  I listed both minor and major chords for V because — it’s probably easier if you hear it.  On your instrument, play an Em, then Bm, then back to Em.  Compare that to how it feels if you play E-B-E.  The V-I progression has such a sense of arriving home, while v-i really doesn’t.  So even though if you really stuck to the minor scale the v should be a minor triad — writers end up changing it a bit to make it a major V, so that going from V to i has a stronger sense of arrival. 

The key takeaway here is that what kind chord (major or minor) a given chord is depends on what the key is.  But, that doesn’t mean you can’t use chords that don’t follow the above table.  In fact, that’s where the fun begins, when you start incorporating chords that aren’t exactly in the key/scale — but that’s for another article.

One addendum that may be confusing.  So we often refer to the chords/notes by number based on where it is in the key/scale.  The note A is the 6th in the key of C, hence the Am chord is noted as vi.  The notes that make up that Am/vi chord is A, C and E.  So in the context of the chord, we call those three notes root, 3rd and 5th.  So when people start throwing around language like “raise the 3rd” or “Major 7th” or “go back to root” you have to clarify whether it’s in the context of the key/scale or the chord.  Bass players, for example, know that “stick to the root” probably means s/he should play the root note of each chord — not that s/he should just play only the root note of the key.


Rhythmic Theory

Thus far we only talked about notes and harmonies, but rhythm is the other critical part of the music.

In Western music, the default setting is to think of rhythm in chunks of four beats.  So a note lasting four beats is called whole note, and from there it breaks up like this:

# of beats 4 2 1 0.5 0.25
Name whole note half note quarter note eighth note 16th note

So when a time signature (also called a meter) of a song is notated as 4/4, it means one chunk (called a measure or a bar, because on a musical score there’s literally a vertical bar that separates measures) of it has four beats, made up of quarter notes.  Other common key signatures are 3/4 (three beats of quarter notes), 6/8, and 12/8, probably in that order.  You can get experimental and try odd-meters – 5/4, for example.

Now, what about notes that last three quarter notes’ worth?  Western music came up with the crazy notion of “dotted” notation to cover for that.  On a score, if you add a little dot to the half-note symbol, all the sudden that half-note gains 50% of its length added — lasting 3 quarter-notes’s worth.  If you add a dot to a quarter note, it lasts for 1.5 quarter-note’s worth or three 8th notes.

One other thing that a beginning songwriter may not understand — there is a concept called harmonic rhythm which simply means that chord changes come at predictable timings.  In many songs a measure gets one chord each, or if it gets two chords it switches in the middle.  Sometimes you stay on a chord for two measures.  You can go against the grain and have unpredictable harmonic rhythm, but know that that creates a very jarring effect.


That covers the majority of use cases of music theory for songwriters in pop/folk/rock/metal genre.  One final point about music theory: it’s a set of concepts derived from patterns used in music that are already written.  They are not rules.  Knowing them can help you analyze the parts that are already written and understand what’s going on — but if you rely solely on music theory as your writing mechanism, your music will be pretty predictable and boring.  What’s described above are what’s common — so by all means start pushing the boundaries. Write a song in 7/8 in the key of C that has a Ab chord, for example.

If I missed any common concepts in music theory, let me know and I’ll add it.  But keep in mind, this is meant to cover just the common use cases — a diminished chord isn’t used very often in typical folk/rock/pop songwriting so I’m not planning to make space for that here.

I hope this primer is helpful in brushing up some basic concepts!  Armed with this fundamental language, now you are ready to acquire skills to write impactful songs.

Image: pippalou


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  2. Excellent primer for the uninitiated, thank you. Plain spoken, understandable and importantly useful. Looking forward to an article around constructing melody over harmonic rhythm/chord changes.

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