Key Signatures

Here's a quick trick to figure out the key of a song.

If the key signature uses sharps, use this mnemonic device:
Cats Go Down Alleys Eating Birds F#requently

So if the key signature is blank, no sharps or flats, its in the key of C major or A minor (we'll leave the minor keys alone for now...)

If it has one sharp (it'll be on the F line) then it's the key of G.

If it has two sharps (one on the F, the other on the C) then it's the key of D, and so on...

If the key signature uses flats, then you imagine that the flats are in a race, moving from left to right. The flat furthest to the right is in 1st place. The guy in 2nd place is the key. Now this doesn't work for the key of F. It only has one flat, on the B line. You're just going to have to remember that one. But all the others work.

Now try it out:
http://www.musictheory.net/trainers/html/id83_en.html

Click on the settings and make sure all of the key signatures are selected, and only do the major ones for now. We'll get into minor keys later.

Do fifty or so and post your results to the comments.