in modern Western music theory, modes use the same set of notes as the major scale, but using a different set of whole and half steps.
At its most basic, a mode of a particular tonic refers to the series of steps to build a scale, and the modes differ in the order of whole & half steps between each note. (it is the pattern of tones and semitones that define the scale)
Each root note & mode will have a corresponding key signature, but different modes can share key signatures – in fact, it is possible to write a scale in each of the seven modes without using any sharps or flats (and so an empty or no key signature)!
X:1
T:D Lydian
K:D lydian
M: 4/4
L:1/4
d, e, f, g, | a, b, c z |]
X:1
T:A major
K:A
M: 4/4
L:1/4
a, b, c d | e f g z |]
For example, the D Lydian & A Major scales both share a key signature – but the root note is different (A vs. D). One way to handle this is to use the key signature of the corresponding (major) keynote, and use accidentals where needed.
Mode vs. major/minor key
The difference between a major/minor key and a mode is which notes are emphasized, and which notes surround the emphasized notes.
In most melodies, the focus of each phrase will be the tonic and dominant of the scale. These are the notes we expect to see at the end of a phrase (in a [[cadence]]), but also:
- used more than other notes
- used on the strongest beats of the bar
- repeated
- accented
- and used in octave leaps