The Architecture of Music

Chords

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12TET

In Western or 12TET (12-Toned 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, A# = Bb (B-flat). These are called enharmonic notes. 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 the book. Please note, there are no B#/Cb or E#/Fb notes. This can best be seen as the two missing black keys 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 2,500 years ago.

Chord Octave and Interval Diagram

Intervals

An interval is the semitone distance between two notes. As can be seen above, the interval between A to E is seven semitones. This interval is known as the perfect 5th. From E to A is five semitones and is known as the perfect 4th. Intervals can be played simultaneously as in a chord or used to describe a progression. Intervals are the same no matter what note you begin from and are considered enharmonic. In other words, the interval is the same between A and A# and C and C# (one semitone).

Interval diagrams are used throughout the 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 as in standard musical notation. They just show the intervals between the notes of chords and scales measured in semitones. Become familiar with the interval diagram above and that it represents an octave and all the notes in between but not the exact pitch of the notes as in standard musical notation.