i've been thinking about putting together a series of youtube videos on these type of subjects. hopefully i'll find the time to do so.
the major scale is really cool in my opinion. not only is it used for picking melodies and leads and things but it also designates which chords fall into a specific key. so i'll try to keep it simple:
the Major scale is a set of intervals. whole step, whole step, half step, whole step, whole step, whole step, half step. i'll denote whole steps with a W and half steps with an H. so for the scale of C Major we get;
(just in case you're not sure a half step is when you go from on fret to the next and a whole step is when you go from one fret, then skip a fret, then play the next.)
C (W) D (W) E (H) F (W) G (W) A (W) B (H) C
C Major is cool and the easiest to understand because it's all of the natural notes (no sharps or flats) basically all of the white keys on a piano. we call the first note in the scale the root, in this case C. if we're going to play a song in the key of C, we typically only play the 7 notes that fall into the scale of C. so this dictates which chords we'll use in a song. for simplicity, lets say all of chords in this key are triads (3 note chords) although we can also use 7th chords and 9th chords and different things which will use four notes. but like i said let's stick with triads for now. in the key of C we'll have 7 different triads and usually we'll number them. so our first triad is going to be the chord of C Major, we get that because C is our root and then to build our chord we'll take every other note after C until we have three notes total. so we have C (then skip D) then we have E (then skip F) then we'll have G. so C major is the three notes of CEG. i like to refer to C as the root, E as the third, and G as the dominate (or 5th if you prefer). you see, we skipped the second and fourth notes. the chords is major because from our root to our third was two whole steps. C (W) D (W) E. see? two whole steps. so C major is our first chord in the key of C and we usually use roman numerals. so we'll call it our I chord.
then for our second chord we'll start with the second note in the scale, which in the scale of C Major is D. so again we'll start with D as the root of our II chord and then take every other note after D. so D (skip E) F (skip G) A. so we get DFA. this chord is D minor. why? because our third is one whole step and then one half step from our root. D (W) E (H) F. that makes it a minor third. remember when we found our C chord it was major because we had two whole steps. that's a major third. and again for our D chord we had a whole step and then a half step, that's a minor third.
and then our III chord is E. E (skip F) G (skip A) B. that's a minor third from E to G so that's E minor.
so i'll just cut to the chase. in the scale of C we end up with C Maj, D min, E min, F Maj, G Maj, A min, and then B diminished or B dim. so i'll explain the diminished chord right quick. the scale repeats infinitely. so the scale of C Major could be thought of as CDEFGABCDEFGABC.... so on and so on. so when we look at our B chord, we start with B and skip every other note. so B (skip C) D (skip E) F. so the B chord ends up being BDF. now remember our 3rd was minor because it was one whole step and one half step from the root. i didn't mention it before but our dominant or 5th note was always three whole steps and one half step from our root (like from C to G). but in this B chord we have a minor third and then our dominate or 5th ended up being two whole steps and two have steps (or just 3 whole steps because 2 half steps=one whole step) instead of three whole steps and half step. so long story short, a diminished chord is almost the same as a minor chord except the 5th is is one half step lower.
so let me reiterate. I=C Maj, II=D min, III=E min, IV=F Maj, V=G Maj, VI=A min and VII=B dim.
you'll notice that I IV and V are Major chords. so it's no surprise that a lot of song have a chord progression of C Maj, F Maj, G Maj, or some combination of those. (especially in country music, blues, rock, hell... lots of music uses this progression).
and your "7" chords will use the same "every other note" type of a pattern, just instead of having a root, third, and a 5th, you skip one more then add another note.... the 7th. so if we're playing in the key of C Major and we want to add some spice and play a C chord with a 7th, we end up with C (skip D) E (skip F) G (skip A) B. so we'll have a chord that has 4 notes and they're CEGB. that's CMaj7. you can do the same thing with all 7 of the chords in the key of C (or any key for that matter).
one last thing, you've been practicing the scale of C Major, so really, you already know all of the Major scales. if you move your pattern up one fret (a half step) you'll be playing the scale of Db Major. move up one more fret (a whole step from C) you'll be playing the scale of D Major. and just to make a quick point, the scale of D major ends ups being... D E F# G A B C#. and to play in the key of D you follow that same "every other note" pattern. so now you chords will look like this;
I=D Maj, II=E min, III=F# min, IV=G Maj, V=A Maj, VI= B min, VII=C# dim. notice the I IV and V chords are still Major. that's just they way the fall when you skip every other note. (every Major key works that way) and your VII chord is always diminished. and II III and VI are always minor. so next time you want to write a song, just pick a key, figure out what chords are in that key, and put together a nice progression. it may be a little faster for you than trying to figure out what chords sound good together by ear. if you stay in key, they're guaranteed to sound good together. but don't be afraid to break the key either and play notes and chords that don't fall into the key. that's where the artist can come out in you. musicians do it all the time. (notice my signature. it's called music theory not music law
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well i hope that wasn't too confusing and at least a little helpful. and i apologize for going on and on. like i said, i've been working on putting together a youtube series to explain some of this stuff in better detail and with videos. (though i haven't posted any yet)
