Music Theory

1. Scales

A scale can be defined as a series of notes, in alphabetical order, going from any given note to its octave and based upon some form of set pattern. The pattern upon which most scales are based involves a set sequence of tones and/or semitones.

On the bass guitar, a tone is two frets and a semitone is one fret. As an example, the B note is a tone higher than A (two frets), whereas the C note is only a semitone higher than B (one fret). Of the other natural notes in music E and F are a semitone apart and all the others are a tone apart.

In music theory a tone may be referred to as a step and a semitone as a half - step. The 3 main types of scales that you need to become familiar with are the chromatic, major and minor scales.

Chromatic Scale — The chromatic scale is based upon a sequence of semitones only and thus includes every possible note within one octave. Here is the C chromatic scale:

The same scale could be written out using flats, however it is more common to do this when descending as such:

Because each chromatic scale contains every possible note within one octave, once you have learned one you have basically learned them all. As an example the A chromatic scale contains exactly the same notes as the C chromatic scale, the only difference between them being the note upon which they commence. This starting note, in all scales, is referred to as the tonic or key note.

Major Scale — The most common scale in western music is called the major scale. This scale is based upon a sequence of both tones and semitones and is thus sometimes referred to as a diatonic scale. Here is the major scale sequence.

Starting on the C note and following through this sequence gives the C major scale:

and in musical notation:

Roman Numerals — are used to number each note of the major scale. Thus F is the 4th note of the C major scale, G is the 5th and so on.

The major scale will always give the familiar sound of DO, RE, ME, FA, SO, LA, TE, DO.

The major scale always uses the same sequence of tones and semitones no matter what note is used as the tonic. The following table lists the 13 most commonly used major scales.

You will notice that in order to maintain the correct sequence of tones and semitones all major scales except C major involve the use of either sharps or flats. You will notice when playing these scales that they all maintain the familiar sound of DO, RE, ME, FA, SO, LA, TE, DO.

Minor Scales — In western music there are three different minor scales. These are the natural minor, the harmonic minor and the melodic minor. Each features a slightly different sequence of tones and semitones as illustrated in these examples using A as the tonic.

A Natural Minor Scale:

A Harmonic Minor —7th note sharpened (called the leading note)

A Melodic Minor — 6th and 7th notes sharpened when ascending and returned to natural when descending.

Of these three minor scales outlined above the melodic minor is the most commonly used. The following table lists the 13 most commonly used minor scales.

Modes — A mode can be described as being a displaced scale. In other words if you play a C major scale but starting and finishing on the D note, you are playing a mode:

This is called the Dorian mode and it is produced by playing through II - II on the major scale (e.g., D - D on the C scale). Each note of the major scale can be used as a tonic (starting note) for a different mode and the situation can be summarized thus:

Modes are commonly used in jazz improvisation.

2. Keys and Key Signatures

When music is talked of as being in a particular key it means that the melody is based upon notes of the major scale (or minor scale) with the same name e.g., in the key of C, C major scale notes (i.e., C, D, E, F, G, A and B) will occur much more frequently than notes that do not belong to the C scale (i.e., sharpened and flattened notes).

In the key of G, G scale notes will be most common (i.e., the notes G, A, B, C, D, E and F# will occur frequently). You will notice here that F# occurs rather than F natural. However, rather than add a sharp to every F note, an easier method is used whereby a sharp sign is placed on the F line (the top one) of the staff at the beginning of each line. This is referred to as the key signature of G major; which is F#.

Here are the key signatures for all the major scales discussed so far.

It can be seen, then, that each key signature is a shorthand representation of the scale, showing only the sharps or flats which occur in that scale. Where an additional sharp or flat occurs, it is not included as part of the key signature, but is written in the music, e.g., in the key of G, if a D# note occurs, the sharp sign will be written immediately before the D note, not at the beginning of the line as part of the key signature.