Scales are the building blocks of tonal music. Scales define "tonality" (the tonal center), are used to build "chords" (groups of notes played simultaneously), define tonal "intervals" (distance between any two notes), and when transposed within a piece of music define a new or temporary "harmonic" center (tonality).
The Major Scale is made up of "Half Steps" (one note moving to the very next note on a keyboard, such as C to C#) and "Whole Steps" (the equivalent of two half-steps). In a Major Scale (also knows as the Ionian Mode), the construction of Half Steps and Whole Steps are as follows. Beginning on the "Tonic" (same note as the key, example: "C" is the Tonic for the Key of "C") we progress from the Tonic (I) a Whole Step up to the (2), Whole Step (3), Half Step (4), Whole Step (5), Whole Step (6), Whole Step (7), Half Step (8 - The Tonic again only one "Octave" up).
Modes use the same scale construction of Whole Steps and Half Steps, but each start on a different degree of the Major Scale.
The Modes also correspond to chords that are constructed based on the scale tones (see the section on chords for more information). Below, the corresponding chords to the modes are shown in (parenthesis).
The Chromatic Scale uses every note on the keyboard. Notice when the notes ascend (go up) sharps (#) are used. When the notes descend (go down) flats (b) are used. The Chromatic Scale lacks a Tonic or Tonal Center and consists of only Half Steps.
The Whole Tone Scale uses every other note on the keyboard. Again, when the notes ascend sharps (#) are used. When the notes descend flats (b) are used. The Whole Tone Scale also lacks a Tonic or Tonal Center, and creates an ambiguous almost mystical sound. Technically there are two (2) Whole Tone Scales. The One shown below starting on "C", and a second one that starts on "C#". The Whole Tone Scale consists of only Whole Steps. There are NO Half Steps in the Whole Tone Scale.
The Eight (8) Tone Dominant Scale is an qui-distant scale. Meaning the pattern of the notes in this scale is one Half Step followed by one Whole Step over and over. This scale can be used with the Dominant 7/#9 and Dominant 7/b9 chords. This scale's cousin, the Eight (8) Tone Diminished Scale has the same construct, except it begins with a Whole Step followed by a Half Step, the opposite of the Eight (8) Tone Dominant Scale.
The Melodic Minor Scale uses one group of notes when ascending and another group of notes when descending. This scale appears often in classical music written in a Minor Key. The first three (3) notes of this scale are the same whether ascending or descending. They differ on the 6th and 7th scale degrees depending upon whether it is ascending or descending. When ascending, the scale is similar to the Major Scale with the 3rd tone played with a flat. When descending, the scale is the same as the Minor (Aeolian) Scale.
The Pentatonic (5 Note) Scale is like the Major Scale, but omits the two (2) Half Steps that appear in the Major Scale, the 4th and 7th Major Scale degrees. This scale creates a less defined sound than the Major Scale as the omitted Half Steps are the magic ingredients that help define a tonal center. This scale is used frequently in Rock music.
The Blues Scale is a different type of scale which is used to play "over" chord progressions instead of "in" the chord progression. For example, if you have a chord progression of C7, F7 and G7, the C Blues Scale (shown below) can be used to play "over the top" of the progression, regardless of which of the three chords are being played. This scale is used in Blues and Rock music.
Altered Scales: From a compositional perspective, altering one or more scale degrees by a Half Step can create a stylistic effect. For example, try lowering the 2nd and 6th degrees of the Major Scale by one Half Step to produce a unique sounding scale. Once you have a working knowledge of scales, playing around with Altered Scales can produce specialized compositions.