Keys VS Modes

Hey Jazz Guy…
What’s the difference between a diatonic key and a mode like super locrian or lydian?—Moded out in Manhattan

Dear Moded:Great Question! This is where some of the terminology of music theory becomes confusing. So you’re not alone in trying to figure this out, to make it worse, many of these words are not always used correctly in common conversation, so it’s no wonder people are confused. Think of it this way: A KEY refers to a particular “home base” or tonic note. For example the “Key of C”. But that doesn’t tell you anything about the rest of the notes that will be used. A MODE refers to a particular set of half steps and whole steps, but does not specify any one tone. So the KEY will tell you what not is the tonic and the MODE will tell you the rest of the scale construction. Lets break it down with an example: Our good old fashion C Major, is called “key of C” but that is a mis-nomer. The truly accurate description of this harmonic system would be the “KEY of C Ionian”. Now I’ve given you a tonal center (c) and a mode type (ionian) that tells you that you will start on C and then go : w w 1/2 w w w 1/2. and then you will be back at C. So Remember, you need BOTH things to tell you what notes to play, KEY and MODE. They are linked. This should also lead you to the idea that practicing in a KEY means you play every MODE and practicing in a MODE means you play every KEY. Hmmm…got a lot of work ahead of you. Good luck!!!