Mode… What’s a mode? Wait… What’s a scale even?? As for me, a scale is a group of notes, for example, a group of notes consists of C D E F G A B is a C major scale, no matter how the notes are played, they are still C major scale. A mode, on the other hand, is a scale played to a certain chord e.g. a C major scale played to a Dm7 chord makes it a D Dorian mode. The concept of mode makes identification easier (knowing what notes to play over different chords) which helps a lot on improvisation and composing as well.
Lets take a look at our favorite C major scale as an example:
Yup. Just a bunch of notes. If we harmonize each note in 3rds to the 7th, we get:
Now we’ve got the chords. If we play a C major scale from the tonic of the chords, this gives us the 7 modes:
So there we have our 7 modes of a major scale! Do work out the rest in all 12 keys!