Why Music Theory?

Music theory gives perspective on how different notes interact with one another. This knowledge is extremely useful when attempting to de-construct music others have played, or constructing ones' own music. This section aims to give an introduction to intervals, chords, keys and scales. Audio is provided so that one may hear the described concepts. This hopefully will enhance understanding.

What is an interval?

(noun) An intervening time or space.

This definition illustrates what an interval is in the literal sense; this definition can also be applied to music theory. Strictly speaking, an interval is the defined space between two notes. There are two types of intervals.

Melodic Interval
An interval where the notes are played separately
Harmonic Interval
An interval where the notes are played together

In Western music theory, intervals are commonly described in terms of their whole steps. It is important to understand the difference between half steps and whole steps. A half step is half of a whole step; it is easiest to invision half-steps by picturing the individual frets on a guitar's fretboard. Each space to put a finger is a half step. Consequently, two of these frets constitute a whole step.

Types of Intervals

There are many types of intervals, but they are easy to memorize if you think of them as ascending half-steps. The table below describes each interval type and how many half-steps it takes to get there. Audio is also provided for each of the intervals, so you can better hear what they sound like.

Table Of Intervals
Interval Name Half-Steps
First 0
Minor Second 1
Major Second 2
Minor Third 3
Major Third 4
Perfect Fourth 5
Augmented Fourth
Perfect Fifth 7
Minor Sixth 8
Major Sixth 9
Minor Seventh 10
Major Seventh 11
Octave 12

First Interval Sample

Minor Second Sample

Major Second Sample

Minor Third Sample

Major Third Sample

Perfect Fourth Sample

Augmented Fourth Sample

Perfect Fifth Sample

Minor Sixth Sample

Major Sixth Sample

Minor Seventh Sample

Major Seventh Sample

Octave Sample

What Makes a Chord?

To put it simply, chords are combinations of intervals that produce a certain sound. Specifically, harmonic intervals make chords because each note in the interval is played in unison. The simplest chord is two notes, while the most complex chords can combine many notes from many different instruments, such as the chords played by orchestras. Because a standard guitar has six strings, six notes are the limit when it comes to chords.


You may have heard the term "key signature". If you played in your middle school or high school band you know what this means, but for folks who haven't, key can be defined as the set group of notes which comprise the chords, melodies, harmonies and other components of musical passages. Songs have key signatures, and so do instruments; for instance, a standard trumpet is in the key of B-flat, while a french horn is in the key of F. Each key signature has a root note called the tonic. For instance, if the key signature is C major, the tonic (or root) is a C; for G-major, the root is G. Key signatures are defined as "major" or "minor". In a major key, the third note from the root is a major third, so if we are in C-major, the third note would be E natural, or a major third above the C. If we are in the natural C minor scale, the third note is a minor third, or an E-flat. Exceptions can be made to these groups of notes, and this is called an accidental.


Scales are intimately related to key signatures in that the key of a song has a scale associated with it. Scales have a set pattern based upon the type of scale; for simplicity's sake, we will discuss the major and natural minor scales. In a major scale, the progression from the root is whole-whole-half-whole-whole-half. So, if we are in C, the C-major scale goes C-D-E-F-G-A-B-C. Notice that there is a half step between E and F. There is also a half-step between B and C. A natural minor scale is the same, but the third, sixth and seventh are changed. What I mean is that in a natural C-minor scale, the progression from the tonic is whole-half-whole-whole-half-whole-half. So, the natural C-minor scale is C-D-E-flat-F-G-G-flat-B-flat-C. Guitars in standard tuning are in the key of E. It can be debated whether it is in a major or minor key, as fingering determines these characteristics.

Audio is provided for the C, G and E scales, in their major and natural minor forms.

C-Major Sample

C-Minor Sample

G-major Sample

G-Minor Sample

E-Major Sample

E-Minor Sample