In the modern western understanding of scales, a mode (or rotation) of a periodic scale is an ordering of the scale's pitch classes determined by choosing one of the pitch classes as the starting/ending point. The chosen pitch class is the tonic of the scale. Together, a tonic and a mode form a key.
Modes are mostly used in the context of tonal or modal music, i.e. as opposed to atonal music, since their definition implies a tonic.
Octave-repeating harmonic series segments are called harmonic modes by several musicians, although this implies a slightly definition of mode.
The diatonic scale has seven different modes. The following table shows the modes of the diatonic scale built on the white keys (C-D-E-F-G-A-B) and in the key of D. The modes can be sorted according to their tonic (sort by note names (white keys)) or their position in the circle of fifths (sort by step pattern)
|Name||Step pattern||Note names
|Ionian (major)||LLsLLLs||C D E F G A B (C)||D E F# G A B C# (D)|
|Dorian||LsLLLsL||D E F G A B C (D)||D E F G A B C (D)|
|Phrygian||sLLLsLL||E F G A B C D (E)||D Eb F G A Bb C (D)|
|Lydian||LLLsLLs||F G A B C D E (F)||D E F# G# A B C# (D)|
|Mixolydian||LLsLLsL||G A B C D E F (G)||D E F# G A B C (D)|
|Aeolian (natural minor)||LsLLsLL||A B C D E F G (A)||D E F G A Bb C (D)|
|Locrian||sLLsLLL||B C D E F G A (B)||D Eb F G Ab Bb C (D)|
A scale has as many modes as the number of tones that it contains within a period. For example:
- the diatonic scale has 7 different modes, because it has 7 tones per period of 1 octave, and 7 possible keys as well;
- the octatonic diminished scale only has 2 different modes, because it has 2 tones per period of 1/4 octave, but it has 8 possible keys, since any of the 8 pitch classes of the scale can be chosen as the tonic.
In an equal-step tuning, any mode of any supported scale can be built on any tone of the chosen tuning, i.e. it is possible to transpose to any key while keeping the same scale and mode. In unequal tunings, each key can have a different scale pattern, therefore different but somewhat similar-sounding modes, which leads to a phenomenon called key coloration.