What do stuff like "6add9, sus2, maj7b5" etc. mean?

I still don't get what all this stuff means. How do you get it? All I know is major and minor, that's all that makes sense to me, but the other stuff doesn't. Can someone explain to me what these crazy things are, where they came from, how you get them, etc.

I would like not to be confused, so try to keep it basic. I am a noob to music theory and a lot of other guitar stuff, I basically taught myself to play.

Ok, chord formulas and their names were really confusing for me when I was learning the basics, but it is honestly really simple! I will try my best to explain this in the most dumbass way, not because I want to sound patronising to you but because it's how I would want it presented.

Right, well you should know that major chords are built off the major scale, minor chords off the minor scale, diminished off diminished, etc?
Well, if you take the Cmaj scale: C D E F G A B, and then number each note in order, you get C=1 (the 1 is properly known as the root), D=2, E=3, etc.
Now play a Cmaj CHORD - what notes are in it? C,E and G, so in other words the 1st,3rd and 5th of the Cmaj SCALE (remember C=1, E=3...)
This 1-3-5 chord setup is the standard formula for chords when you apply it to that chord's corresponding scale, e.g. 1-3-5 of the major scale, minor scale etc...
However, what happens if instead of using 1-3-5 to build a chord, we replace the 3 with the 2 creating a 1-2-5 formula? This is known as suspending the 3rd, and doing so creates a sus2 chord (sus is short for 'suspended'). The same can be done by replacing the 3 with 4, creating a sus4 chord. Furthermore, we can also replace the 3 with both the 2 AND 4, which creates a sus2sus4 chord.
So, if we were to take our standard Cmaj chord and apply these suspended formulas to it, we could get Csus2, Csus4 or Csus2sus4.
Does that seem pretty straightforward so far?

Afro

I totally get what you mean by each note having a number to it. That makes a lot of sense to be, the "swapping" thing I don't totally get though. Um, how does that work? Does the 3 become 2 and 4 because it sounds better in the scale or something

It's done just to make the chord sound different. Adds a bit of variety.

I thought that all chords were built off the major scale, and the chord formulas are relative to the major scale, for example major = 1, 3, 5, minor = 1, b3, 5, etc

Yeah he was wrong in saying that. They are all built off the Major scale.

I'm just going to reiterate what has already been said.

Intervals are labels for organizing notes. The Major scale has 7 notes/intervals. The use of intervals could be seen as a universal way to organize music. Intervals are like the math formula's of music. Although you can memorize the numbers yourself and never use the formula, it is the formula that connects all the seemingly random numbers and can make figuring out such numbers quickly. So back to music. Instead of learning every note in all 12 Major keys, you learn the intervals and you can apply that to create all 12 Major scales without learning each and every note. Although, don't get me wrong, it is helpful to have memorized the notes.

To build a chord, we use the major scale pattern. From seven intervals we pick out certain ones, sometimes adjusting the notes to fit our liking. These adjustments also fit into other rules of theory, etc. but we'll just stay simple.

The name of the chord tells you what to do, universally. To know what they tell you, just look them up. If you go to the guitar chord page, and select chords, on the left, you will see a list of the intervals used to create such a chord.

You will see everything can branch off of the Major chord, 1, 3, and 5;
Major:
1 3 5

The minor chord simply flats the 3rd,
Minor:
1 b3 5

As we continue on, you will see the Major chord's intervals are the original structure, but we build off of other chords such as a Major 9
Seventh chords add on a seventh,
Maj Seventh:
1 3 5 7
Min Seventh:
1 b3 5 b7
Dominant (7th):
1 3 5 b7
Maj 7 b5:
1 3 b5 7

Some of the names are obvious (such as the Major 7 b5: Take the major chord, add on a 7th and flat the 5). Others are labeled with names you will have to memorize their meaning. (Dominant is the Major chord with a b7).

For a mini lesson on Seventh chords see,
http://www.all-guitar-chords.com/lesson.php?id=50

Anyway, the whole point of the names and different selections of intervals is to convey a different tone. each chord has it's own sound, even when you play inversions, or leave out a few notes, the chord changes. In the end, it is our minds which we follow.

Here are other types of chords,

Diminished:
1 b3 b5 bb7
Half Diminished:
1 b3 b5 b7

Augmented:
1 3 #5

As we continue on, you will see the Major chord's intervals are the original structure, but we build off of other chords such as a Major 9 which incorporates the Major's intervals, the Seventh's structure and adding a 9th.

Ninths, take the major chord, adjust it according to the title, then add on a seventh(according to the title) as well as a 9th.
Major 9:
1 3 5 7 9
Minor 9:
1 b3 5 b7 b9

For Sus (suspended) chords, we "suspend" the 3rd and fill it in with a 2nd or 4th interval,
Sus(pended) 2nd:
1 2 5
Sus 4th:
1 4 5


Adding another interval to the mix without adding a seventh? Such as a Major6 add 9. "Adds" are a no brainer huh?
Add 9:
1 3 5 9
6Add 9:
1 3 5 6 9

Hope we've helped you. Cheers.

I think it depends where you get your information from. My music lecturer at college has always tuaght me that major chords come from the major scale, minor from minor, etc. and as he has a PhD in music I'm inclined to agree with him. But BHS's method works perfectly as well, and using either method still gives the same result. Personally, I find my method more helpful when it comes to using extensions on the chords, just because I have the relevant notes sat in front of me.

Afro