18.4What is a mode?

Take the notes of C major:

C D E F G A B

But make a different note feel like home.

Start from D:

D E F G A B C D

That produces:

D Dorian

Start from E:

E F G A B C D E

E Phrygian.

Start G:

G A B C D E F G

G Mixolydian.

Same note collection.

Different tonic = different interval structure and musical character.