Difference between scale and key?

Originally, I thought that key and scale were essentially the same thing. I thought “key” was just a way of saying that (for the most part) we will be using notes from a certain scale. Maybe, C major, maybe B minor etc… But, the more I’ve studied theory there seems to be a deeper, more fundamental difference between the two.
For example, apparently you can use multiple scales within one key. I don’t understand why the key of C major would be called C major if you can use notes from other scales… My first thought would be that multiple scales can use the same notes, which makes sense. But, then my next question would be, can you use notes outside of the C major scale in the key of c major?
I’ve also heard “it all has to do with the concept of tonality”. I have a vague understanding of tonality, so how specifically does tonality determine what can be played or should be played within a certain key?
I feel like if I’ve learned anything in music theory it’s that there are a lot of rules, but even more exceptions to the rules. Just saying that so you know I get that your answer probably won’t be as cut and dry as I’m asking haha

Honestly I think scales are specifically determined by musical theorists to be functional in composition… meaning they can be used as a part of a solo…as for key a song usually starts off in a specific key and can change key by using a different chord progression…but heres the thing…

I know you just trying to understand certain things but honestly these rules and theory are more of loose guide to help a person translate their imagination into audio form…

So just use your imagination try writing a few songs…either with an instrument or some sine saw triangle and square wave in a daw/hardware synth…

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Do you think music theory can enhance creativity at all?

Yea I do…just Google some music theory…and then write a song using the music theory that you’ve learned

Musical Theory is to music like grammar and vocabulary are to a language. You can speak and even write without knowing much, and are understandable even when using it incorrectly. The more you know though, the better you can express yourself.


There’s definitely value in learning some music theory. The basics of keys, circle of fifths, and basic harmony can get you very far and ‘unstuck’ you when you’re writing something.

Now if I understand you correctly, when you say multiple scales for the same key, you’re probably referring to modes. Modes are offsets for where the root note is for a given key. Normally in C Major (Ionion Mode) the root is C. In D Dorian (which is also using the same notes as C Major) the root note is not C, but D. Likewise E Phrygian (which is also the same notes as C Major) the root is E.

If you play these as scales you may feel a different kind of pull in the way the root note resolves. In Ionion the B to C is a half-step resolution. In Dorian it is a whole step and doesn’t have as strong a pull. In Phrygian you have the same, but you also have the II (second note - F) being a half-step away (as opposed to normally having the II note being a whole step away).

These different modes also use different harmonies. In C Major the typical functional harmony applies with Dominants (G Major) and Sub Dominants (F Major).

In Dorian there is no iv or V chord. Normally in D Minor you would have G minor and A Major, but neither of these chords exist in D Dorian. Instead you have ii(E Minor), III (F Major), IV (G major), v (A Minor), VII (C Major). This gives a very different kind of harmony and feel compared to C Major.

Phrygian is even weirder with the flat 2 scale degree. (flat 2 because the second note F is a half step away, instead of the traditional whole step, hence it is flat).

Here are some examples of how different the harmony feels with different modes:

Lydian (4th Scale Degree as root)

Mixolydian (5th Scale Degree) - in this case E Mixolydian translates to the same notes as A Major.

Now some of this you may not find very useful, again it depends on your goals and what you’re looking to get out of theory. But the theory is mostly meant to open your mind to different ways and possibilities of expressing music. You can even create your own exotic scale with your own set of modes and write entirely original music around it if you so desire.