Ok, so we know how to read music, we know about keys and scales, and we know about intervals. So what about chords? Most people, especially if they play guitar, are going to know about chords, probably that there are minor, major, 7, and power chords. But that doesn't really tell us too much. I mean, that tells you all you need to play maybe 90% of rock music, but it doesn't tell you the why to anything.
Now, since we know that certain intervals can be major and minor, and chords can be major and minor, they're obviously related, right? They are, but not quite as obviously as you'd think.
Also, before I go on I should mention that I'll start using some shorthand to refer to intervals, so I'll quickly go over them:
The number is the interval, so a 3 would be a third. A 5 would be a fifth. Etc.
The letter/symbol is a little specific:
M = Major
m = minor
aug = Augmented
dim = diminished
So, what are chords? Chords are combinations of 3 or more different pitch classes. With those, you have two or more stacked intervals. Also you can measure an interval between the lower and upper note. To make this a little clearer, let's look at one.
So between C and E there, we have a Major third. Between E and G there's a minor third, and we can measure a Perfect Fifth between C and G. Also, this particular type of chord is called a "Triad". A triad is any chord of two stacked thirds, and is probably what you'll see most often for a lot of music, unless you play jazz or grunge that has its own sets of standard chord construction.
Now you'll notice that the chord I posted has both a Major and minor third. So which is it? Major or minor? Major-minor(This is also technically correct, but no one would say it)? And what would happen if we had two Major or two minor thirds? Would it be super-Major? What if it had a fourth? Or a fifth? Holy crap!
Well, it turns out this is our intro to one of the annoying things about theory. For a grand unified system that catalogs and explains like, everything in music ever, there isn't always a standard rule. A lot of things with theory everything behaves in some standard fashion, and sometimes we just have nomenclature that you have to pretty much just learn. There are still patterns and some ways to go about thinking about the whole thing that make it a little easier, but not so much a hard fast rule that everything obeys. I'll try to give as many ways to think about this as possible, so hopefully at least one will click.
So we know of 4 different interval types, Major, minor, Augmented, and diminished. To start off, let's look at the relations between thirds in different triads.
Let's for now only deal with Major and minor thirds, as, as I'll get to when talking about inversions, pretty much any triad can be boiled down to combinations of thirds. In order, let's say we start stacking minor thirds. A minor third on top of a minor third is a "Diminished" chord. I know, there aren't diminished thirds in a diminished chord, but the chord is diminished. Building from the root(The root is the bottom note of a chord when in the form of stacked thirds, it's also the note that we use to name the chord) up, if we have a minor third and then a major third, it's a minor triad. Building from the root up if we have a Major third and then a minor third, it's a Major triad(Such as the example up there), and if we stack major chords it's an Augmented triad. Ok, that's simple enough, though it doesn't really explain why diminished or augmented chords are called that. However, it does lay the groundwork for looking at chords with more notes than triads, like 7ths.
So let's look at the intervals from root to third and from root to fifth(In general, when talking about notes in a chord, we go by the scale degree if we were in the key of the root. That sounds confusing, but essentially think that in C Major, with a d minor chord, f would be the third of the chord. It's hard to explain but it does make sense and work out). If we have a minor third and a diminished fifth, the chord is diminished. If we have a minor third and a Perfect fifth, the chord is minor. If we have a Major third and a Perfect fifth, the chord is Major, and if we have a Major third and an Augmented fifth, the chord is augmented. This way makes a lot more sense, but part of that's because we're just ignoring half of the internal intervals, and when we add 7ths to chords this method falls apart a little bit.
Another way to think about it that sort of bridges the two, is if the fifth is unaltered, kind of pretend it doesn't exist, because it's not really giving the chord any value. A perfect fifth is like, the quintessential "Open" sound, without any specific sonority. So if you have a major third, it's a major triad, and a minor third makes it a minor triad. The difference between it just being a third or a triad is the existence of the fifth, but the fifth doesn't do anything to the chord. If the fifth is altered to make the chord smaller, it's diminished, and if the fifth is altered to make the chord bigger, it's Augmented.
And finally, we have the scale degrees above root with modifiers. So 1 - b3 - b5 is diminished. 1 - b3 - 5 is minor. 1 - 3 - 5 is Major. 1 - 3 - #5 is Augmented.
Ok, hopefully one or all of those ways to think about this stuck, so we can move on to inversions, and then 7ths.
So what if there's a P4(Perfect 4th), in there? There's nothing in any of those guides that accounts for a P4. Well, let's take a look at something:
Ok so. What is this? It's got a minor third and... a perfect fourth. The interval between the... root? and.. fifth? is a minor sixth. What?
Well what are those notes? E, G, C? Where have we seen those notes before? What if we take that top note and throw it on the bottom? Hey we know that chord! Yeah, so that picture is a C major chord, just rearranged a little. This is what's known as an inversion. Inversions give a different sound due to their different bass note, and once we get to voice leading, can make bass lines move more smoothly than just always being on the root.
If the bottom note of the chord is the root, so C-E-G for our example, then it's in "Root position". Pretty simple. If the bottom note is the third, then we're in "First inversion", and if the bottom note is the fifth, we're in "Second inversion". We haven't talked about roman numerals for chords yet(and it'll be a few updates yet), so for now we'll deal with probably how you've seen inversions and different bass notes, with a slash. So C/E for instance indicates a C major triad with an E in the bass, or first inversion. Now, some of you may notice that they're not exactly the same thing... sometimes you play the chord in root position in the right hand or on the guitar, for instance, and then like two octaves below that the bass player is sitting on their open 4th string and is that really the same as a stacked m3(minor third) and P4? Well, as far as sound is concerned, not really, but as far as we're concerned with analysis pretty much, yeah. Sometimes the bass note doesn't fit in the chord either, but that's a whole different bucket o' worms.
For those of you who haven't seen "C/E" or have any idea what that is, we'll cover that really soon, but first let's talk about 7ths.
So, triads we've got, they pretty much only come in 4 varieties. What if you add another note?
I apologize for that example, it was the only Major 7 chord I could find without having to search around too much or go through more shit than I want to for a single chord to come from Finale. But let's look at the notes there. G-B-D-F#. Allright well that's four notes. And what are the intervals? Stacked we've got M3-m3-M3. Above the root it's an M3, P5, M7. Now, with an extra interval in there over triads, we have more combinations of minor and major thirds we can combine. I'll just give you guys a list here of what the different 7th chords are, starting with the most diminished going to the most augmented:
Stacked thirds | Intervals above root | scale degrees with modifier : Designation
m3-m3-m3 | m3, dim5, dim7 | 1, b3, b5, bb7* : Fully-diminished 7
m3-m3-M3 | m3, dim5, m7 | 1, b3, b5, b7 : Half-diminished 7
m3-M3-m3 | m3, P5, m7 | 1, b3, 5, b7 : Minor 7
m3-M3-M3 | m3, P5, M7 | 1, b3, 5, 7 : minor-Major 7
M3-m3-m3 | M3, P5, m7 | 1, 3, 5, b7 : Dominant 7
M3-m3-M3 | M3, P5, M7 | 1, 3, 5, 7 : Major 7
M3-M3-m3 | M3, Aug5, M7 | 1, 3, #5, 7 : Augmented Major 7
M3-M3-dim3 | M3, Aug5, m7 | 1, 3, #5, b7 : Augmented 7 (This one's really hard to remember and stupid)
*No that wasn't a typo, that's a double-flat. Double-flats behave pretty much like you'd expect them to... they're two semitones down. So essentially they're a whole step down. For double-flats, you just have two flat signs in a row, and for double sharps you have sort of an x. In fact, an x will work in text.
Ok, I've got go meet a vocalist to go over part of a studio recital, so we're going to end the lesson now, but I want to as a last thing go over the ways of writing the modifiers for chords, in case you see these symbols and don't know what the hell they mean:
Major Triad: M, Maj, Nothing(For instance, C would just be C Major)
minor triad: m, -, min
Augmented triad: Aug, +
Diminished triad: dim, o
Major 7: M7, Maj7, Δ(In my life, I have never seen that one used.)
minor 7: m7, min7, -7
Fully Diminished 7: o7
Half Diminished 7: ø7, m7b5, -7b5
Minor-Major 7: mM7, mMaj7, mΔ7, -Δ7(Again, those last two... I've only seen them in books, never on a score)
Augmented Major 7: Maj+7, Maj7#5, M7#5, Δ+7
Augmented 7: +7
Those triangle ones.... maybe as I think back I've seen them on one Jazz chart, but it's very rare. Mostly if you remember that + is augmented, o is diminished, m is minor, M is major, you're pretty good.
Also, finally, alt bass notes... I said I'd explain that. When dealing with absolute chord notation like I have been so far, that is to say, not measuring with roman numerals, just the notes of the chords, if we have something like dm/F the F is the bass note, and we read that as "D minor over F", or "D minor, F bass" or "D minor, 1st inversion".
So if we see "D", we play a D major chord. If we see "F+7" we play an F Augmented 7 chord. If we see "Aoaddb6", we play an A diminished chord and add in a flat 6(F, in the example). For anything not covered by the symbols, you'll often see something like "b5" in the chord designator, which really just means whatever else you're doing, flat the 5.