The notes of the major key are determined like this: root, whole step, whole step, half step, whole step, whole step, whole step, half step (1 octave above the root).

In the diagrams below, whole steps are denoted as “W” and half steps are denoted as “H.”

The notes of the natural minor key are determined like this: root, whole step, half step, whole step, whole step, half step, whole step, whole step (1 octave above the root). There are actually two more types of minor keys, but this is the main one worth knowing.

If you’re able to play an instrument, learning how to play scales can be very useful. This makes them much easier to memorize and much easier to recall when working.

And you don’t have to be a virtuoso instrumentalist for this to help. The ability to play an instrument will make music theory more “real” for you and much less abstract.

Chords

A chord is a collection of three or more notes played simultaneously. In composition, different chords can be played consecutively (a progression—we’ll get to that next) to move the piece along.

Each chord in the sequence sustains for a certain amount of time, locking the measure(s) on that chord. Melodies can be built from the current chord.

Chords are generally built by adding non-adjacent notes from a scale. The number of notes we include in the chord determines its sound and how we notate it.

Triads

Stacking three non-adjacent notes from a scale creates a triad. This is the most basic type of chord, as the root, third, and fifth are enough information for our ears to identify a certain chord.

In the key of C Major, we could start at C (first note of the scale) and add E (third note of the scale) and G (fifth note of the scale) to create a C Major triad.

Major vs. Minor

While we’re at it, the distinction between major and minor chords is important to understand. Take a look at the major and minor scales below.

Notice that the third note is different in the two scales. This note is a half step lower in the minor scale than it is in the major scale. Building a triad starting on the first note of each scale would create one starting with a major third and one with a minor third.

These chords, as you could expect, are called a major and minor triad, specifically a C Major triad (or just C Major) and a C Minor triad (or just C Minor).

Seventh chords

A triad obviously isn’t the only type of chord. We can skip over another scale note (whether we’re in major or minor) and add the seventh note of the scale to create a seventh chord. This added note introduces a new tone to the chord, making it more complex and changing it.

Inversions

A chord’s notes can be played in any octave without changing its identity. This is done through the use of inversions. The same notes are used, but each inversion has a slightly different sound.

The shape we’ve talked about for triads and seventh chords is referred to as “root position," as its lowest note is the root of the chord. We can move the root note up an octave to create the same chord in “first inversion." This will still function as the same chord, but sound slightly different.

The third can be moved up an octave for “second inversion."

The fifth in seventh chords can be moved up for “third inversion."

Triad:

Seventh chord:

Inversions can be used for smooth “voice leading." This is the concept that each note in a chord should lead seamlessly to a note in the next chord. By using inversions, this standard chord progression sounds much smoother because individual notes within the chords jump around less.

Progressions

Chord progressions are the basis of harmony in music.

Like melodies, they are very dependent on the key. Melodies are usually made from the available notes in a key, while progressions are created mostly from available chords in the key.

These available chords can be found by creating root-position triads and seventh chords rooted on each note in the scale.

As you can see in the C Major key below, our available triads are C Major, D Minor, E Minor, F Major, G Major, A Minor, and B diminished.

Note: A major triad is built from two thirds, a minor third stacked on a major third. The minor triad is a major third stacked on a minor third. A diminished triad is two minor thirds stacked. Two major thirds creates an “augmented” triad.

Chords in a key can be described with numbers as well, just like the notes in a scale are. Most chord notation uses Roman numerals, with major chords being capitalized and minor chords being lower case.

The major key (starting at any root) includes the chords I, ii, iii, IV, V, vi, vii° (° is the symbol for diminished).

The minor key includes i, ii°, bIII, IV, v, bVI, bVII.

With the terminology and notation in mind, let’s look at some common progressions. Keep in mind that a chord progression can be as complicated or as simple as you’d like. It can be anything from two chords on loop to a totally linear sequence that doesn’t repeat.

Major progressions

There are a few standard progressions in the major key that are worth knowing and understanding. The first is arguably the most common in Western music: I - IV - V - I

In the key of C Major, this is C Major, F Major, G Major, C Major.

This progression is and has been used extensively across many genres, especially in classical and gospel music. As such, it can also be heard in styles that developed from these genres, such as blues and rock.

Elvis Presley - “All Shook Up” (starts on I, IV - V - I happens at 0:20)

Counting Crows - “Mr. Jones” (especially noticeable in chorus @ 0:41)

The classic I - IV - V - I progression demonstrates a key aspect of resolution. This is the concept that certain notes / chords in a key sound like they lead (or “resolve”) to other notes / chords in the key. Theoretically any chord can come after another, but some resolutions sound more powerful.

The I chord represents the current key, and is called the “tonic” chord.

The V chord is called the “dominant” chord. It has the strongest pull towards the tonic. In the key of C Major, this chord is G Major, containing notes G, B, and D.

The important one here is the B, which is one half step below C, the root note of the key. This note is referred to as the “leading tone," which resolves heavily to the root note. This is why V sounds like it resolves so strongly to I.

Another standard major progression is I - V - vi - IV - I. This is the classic “four chord song” progression, which has been used in pop and rock music for decades. The video below demonstrates just how prevalent this progression is:

In the key of C Major, this is C Major, G Major, A Minor, F Major, C Major.

Notice that the resolution at the end of the progression is different. This is because a resolution from IV to I instead of V to I has become a characteristic sound of contemporary music. How you resolve to the tonic will greatly determine whether your progression references more contemporary or more traditional music.

Minor progressions

Now that we have new chords to work with, the minor key has a whole host of new available progressions. We can create a brand new progression by taking any of the major progressions and changing them to minor progressions.

Simply alter any of the notes that change when going from major to minor (3 becomes b3, 6 becomes b6, and 7 becomes b7).

Here are the two examples from above, now in minor:

I - IV - V - I becomes i - iv - v - i:

i - iv - bVII - i

i - bVI - bVII - i

Conclusion

While it may seem like a daunting challenge to learn music theory, a bit of fundamental knowledge can help musicians connect with each other, making them more able to “speak the language."

With some of the information above and a handle on the terminology, music creation can be a much less random, much more intentional process.

And further, an understanding of music theory helps to legitimize an artist as a “musician." In the age of the Internet and the endless waves of new artists, developing this musicianship can truly set someone apart from the rest of the crowd.

In the end, this will make the artist more effective and versatile, opening up opportunities to continue moving up in the music industry.