Here's my (first) contribution to music theory on this forum.
A lot of players I've met are unfamiliar with key signatures, and don't know much about the value of the Circle of 5ths. Attached are two PDFs - the first one is a chord chart, the second PDF has additional chords along with a fretboard chart, a Circle of 5ths, and a list of key signatures.
Here's what's cool about the circle of 5ths...if you can tell time with an analog clock, you already know more than you think about music theory. Memorize the key signature names on the circle. They are arranged so that the fifth note of any key is the root (or first note) of the next key moving clockwise. The keys on the outside of the circle are "sharp" keys, those on the inside are "flat keys." If "C" is at the "zero" hour (no sharps/no flats), G is a one o'clock (and has 1 sharp in it's scale/key signature), D has 2, A has 3 and so forth. The flat keys work counter-clockwise - F has one flat, Bb has two, Eb has three, and so on.
Here's something else that's cool...did you know that (when you arrange scales in order of the Circle of 5ths, that the last four notes of ANY major scale are the same as the first four notes of the next scale? These four-note patterns are called "tetrachords" (Greek: "tetra"=four, "chord"=note).
And something really useful - Look at the circle. Pick any letter...it will represent the key you want to use for your song. The selection that is counter-clockwise one space is the IV chord, and the one that is immediately clockwise is the V chord. This is HUGELY useful when transposing from one key to another. Let's say you've got a song you know in the key of "A" - look at the circle. A I-IV-V-I progression would be A-D-E-A. Wanna transpose? Pick a new key...let's take something a little off the wall, like Bb. According to the Circle, Your new chord progression would be Bb-Eb-F-Bb.
Relative minors to a major key are always three notches up on the circle. In other words, the relative minor to the key of C is the key of A minor...three spaces clockwise on the circle.
Here's a useful bit of knowledge for you when your chart has a diminished 7th chord in it: did you know there are only three different diminished 7th chords, period? If you look at a piano keyboard, start at any note, count up three half-steps (or on a string, go up three frets). Do that three times, and you have the notes in a diminished 7th chord. Do it once more, and you're back to an octave above where you started. The notes in a dim 7th chord divide a 12-tone scale into four equi-distant intervals. 12/4 = 3. The only difference in a C°7, an Eb°7, a Gb°7 and an A°7th is the root - the note on the bottom of the chord. (Don't know which chord to play? As long as you finger it right, you have a one-in-three shot at getting the right Dim7th chord.)
If this info is helpful to anybody, let me know.
- Brad Kozak