The Architecture of Music


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In Western or 12TET (twelve-tone equal-temperament) music there are twelve notes, or twelve divisions in sound, we hear as equal steps in pitch in an octave. They are named alphabetically in ascending pitch order as follows: A, A# (A-sharp), B, C, C#, D, D#, E, F, F#, G, G#. On a guitar, each fret represents one half-step or semitone. A whole-step is equivalent to two half-steps or two semitones. Study the octave diagram below: an octave is the twelve-semitone distance between repeating notes (A to A, B to B, etc.).

Every sharp note can also be referred to as a flat, eg. A# = Bb (B-flat). These are called enharmonic notes and sound the same and are played on the same place on any instrument. Sharp and flat symbols are used to condense transcribed music to fit twelve notes onto the five lines and four spaces of standard musical notation. For simplicity, enharmonic flat notes are not used within this book. Please note, there are no B#/Cb or E#/Fb notes. This can best be seen as the two missing black notes on a piano. Notes do not skip semitones because these two notes do not exist. These missing notes are just a result of how the notes were named over the course of thousands of years.

Interval Diagram


An interval is the semitone distance between two notes. As can be seen above, the interval from A up to E is seven semitones. This interval is known as the perfect 5th. From E up to A is five semitones and is known as the perfect 4th. Intervals can be played simultaneously, as in a chord, or can be used to describe the motion of a chord progression. Intervals are the same size no matter what note you begin from: for instance, the interval from A up to A# and from C up to C# are both one semitone.

Interval diagrams are used throughout this book instead of standard musical notation to show the underlying architecture of chords and scales. They do not show the pitch of the notes to be played; there is no standard musical notation. They just show the intervals, measured in semitones, between the notes of chords and scales. Become familiar with the interval diagram on the following page as it is used extensively throughout this book.