Accidental Order

The Circle of 5ths tells you that there are 3 sharps in the key of A.  It does not tell you why.  Here's the WHY part.

More Scales than a Fish

That’s how music must seem.  Every time we blink, someone has a new scale to suggest.  The familiar, Ionian mode (do re me fa so la ti do) and the Aeolian mode (la ti do re me fa so la) dominate popular music.  But folk music makes good use of other modes including Dorian and Mixolydian.  One would think that should be enough.  But, really, how much of a good thing is enough??

Here are some additional scales to put into your inventory.