Diatonic and Chromatic Scales
Half Steps
In the keyboard lesson we learned that half steps (or semitones) occur between adjacent keys on the keyboard. A half step is the smallest possible distance between two pitches. We also learned that pitches can be given more than one name. For example, the pitch E♭ can be enharmonically re-spelled as a D♯. Now, let's combine those two concepts to see how half steps can be either diatonic or chromatic.
Starting from the pitch A on the keyboard, the adjacent black key to the right could be called either a B♭ or an A♯ (both of these options are shown in the example below). If we were to call the second pitch a B♭, the half step between A and B♭ would be a diatonic half step. A diatonic half step involves two different letter names, with one pitch notated on a space and the other on a line (click on "Diatonic" in the example below). If, on the other hand, we were to spell the second pitch as an A♯, the half step between A and A♯ would now be called a chromatic half step. A chromatic half step is a half step between two pitches with the same name, notated on the same space or line (click on "Chromatic" in the example below).
Remember:
- Diatonic half steps involve different letter names and staff positions.
- Chromatic half steps involve the same letter names and staff positions.
Whole Steps
A whole step is the equivalent of two half steps. For example, if we were to move up on the keyboard from A through A♯ to B (two half-step moves), that would be a whole step (as shown in the example below).
A whole step from A, to A♯, to B
Although it is possible for a whole step to involve two pitches with the same letter name (such as the whole step between A♭ and A♯), we do not refer to whole steps as chromatic—that is a term reserved for half steps. In the scales that we will be building, whole steps will always involve notes with two different letter names.
The Chromatic Scale
The chromatic scale is made up entirely of half steps, dividing the octave into twelve equal semitones and using every key on the keyboard within an octave span (C to C♯, C♯ to D, D to E♭, and so on, as illustrated in the example below). The chromatic scale is sometimes called the twelve-tone scale, since it includes all twelve of the notes used in the Western musical system. The word chromatic comes from the Greek word khromatikos, meaning "color." Passages of music that are based on the chromatic scale are sometimes described as being very "colorful."
The chromatic scale
There are different ways of spelling the chromatic scale, as illustrated in the two examples below. The first example uses only sharps and the second one uses only flats (click "Show Me" to hear these scales played). You can also mix sharps and flats, as illustrated in the example given above. But since there are twelve notes in the scale, and only seven available letter names, the chromatic scale always has five chromatic half steps between notes with the same letter name. (In the example above, these are: C to C♯, E♭ to E, F to F♯, G to G♯, and B♭ to B).
Chromatic Scale Using Sharps
Chromatic Scale Using Flats
Diatonic Scales
By contrast, diatonic scales do not contain any chromatic half steps. They are made up entirely of diatonic half steps and whole steps. The word diatonic derives from the Greek word diatonikós, meaning "through the tones." In a diatonic scale, we step through all of the tones, using each of the seven letter names only once. For example, in the scale shown below, the letters A, B, C, D, E, F, and G are used only one time (with the initial A repeated at the top). In a diatonic scale, it is not possible to use different enharmonic spellings (such as a B♯ instead of a C) since this would result in a scale with duplicate letter names (in this case, two Bs and no Cs).
Diatonic scale
Remember:
In a diatonic scale, each of the seven letter names is used once and only once.
The major scale and the minor scale are the two scales most commonly used in Western music. Both of these are seven-note diatonic scales, using each of the letter names only once. Both of them are based on alternating patterns of whole steps and diatonic half steps. The position of the half steps in these patterns makes the two scales sound different from each other.
There are other types of diatonic scales, such as the church modes (Dorian, Phrygian, Lydian, and Mixolydian), but for now, our focus will be on the major and minor scales, since so much of Western music is based on these two scales alone. We will begin by looking at the major scale.