Scales and the chromatic pitch brackets

Pitch brackets change the pitch of the melody line by adding or subtracting scale steps. But which scale? Major or minor diatonic, chromatic, pentatonic? Do pitch brackets work equally well for all scales? How do pitch brackets add or subtract chromatic steps to diatonic scales? These are important questions which I will address in this post.

The concepts of pitch bracket and melody line are independent of any particular scale. Rather, the melody line carries a pitch value from note to note. A pitch bracket simply changes this pitch value at a certain position along the melody line. In the diatonic scale, the octave is divided into 7 steps and so pitch values range from 1 to 7. In the chromatic scale, there are 12 steps and so pitch values range from 1 to 12.

Consider the two chromatic pitch brackets above. The “C” shaped chromatic pitch brackets add or subtract semitones to the melody line. The c1 bracket adds one semitone while the c2 bracket adds two semitones.The diatonic and chromatic scales are shown below. The notes of the scales would be placed between the brackets but are omitted here.

All diatonic scales have five tones and two semitones. The tones correspond to c2 brackets and the semitones to c1 bracket. Now we can render the diatonic scales using chromatic pitch brackets. In the major scale the order of tones and semitones is T T S T T T S.

In the minor diatonic scale, the order of tones and semitones T S T  T S T T.

I should note that the diatonic and chromatic pitch values are separate values. While both kinds of brackets can be placed on the same melody line, diatonic brackets only modify diatonic pitch values and chromatic brackets only modify chromatic pitch values. This is not unlike staff notation. For example, a double flatted E may have the same pitch as D but it still retains the diatonic identity of E, only with a chromatic modifier applied.

The last two melody lines above probably look familiar to you. If you squeeze the brackets together you form a keyboard which is mirrored across the melody line. In a following posts I will show how chromatic pitch brackets help us understand some elements of harmony.



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