OK, so, now let's take another look at our friend, the C13b5b9. Here's that same, sad, little tab from before
And, again, that's the Gb, Db, Bb, E, A voicing.
So, what is an X13b5b9? Well, let's break it down a little. A 13 chord is a dominant type chord. This means it starts with a major triad, and then has a minor 7th (just the note, just an interval) stacked on top. Shall I get a little more basic? Chords are built by taking every other note of a scale and stacking them. If your three-octave scale (in the key of C) goes like this:
C D E F G A B C D E F G A B CD E F G A B C
your chords would be formed from a thing that looks like this, by dropping every other note from the scale:
C _ E _ G _ B _ D _ F _ A _ C _ E _ G _ B
That's got most of the diatonic (in the scale, no accidentals, no extra sharps and flats) chords in the chord scale, by starting on the note in question and taking the next two or three or more notes. Like, to form the diatonic C chord in the key of C, you start on C and move up.
C _ E _ G
That makes a C Major Triad, or, you just keep going:
C _ E _ G _ B _ D _ F
That makes a C Major11. This is because, once you cross the Octave (the 8th note in the scale), you keep counting. So, the triad is the First, Third and Fifth degree, or note, of the scale. The Major 7th is that major triad, with a Major 7th interval on top. From there, you pass the octave, and get the note that was the second, an octave higher, and which has crossed his name off his nametag and is now pretending to be named 9th. The fourth becomes the 11th, and the sixth becomes the 13th. At this point, if you're counting, you have a chord that looks like this:
C _ E _ G _ B _ D _ F _ A
That's all the notes of the scale. If you drop the top half of them down an octave, you're just leaning on the keys of the piano. How could that possibly sound good? Well, if you arrange it more or less as it is there, it's just a C Major triad and a B "half-dimished" 7th (just roll with it) stacked, and it's got a neat, jazzy almost-dischordant quality to it.
So, what's the difference between a Major 7th and a Dominant 7th? They are the same, but you drop the 7th degree by a half step. Then, if you go ahead and count up the scale, you get a thing that looks like this:
C _ E _ G _ Bb _ D _ F _ A
Which is a C triad and a Bb Major 7th chord stacked, which makes a C13. Any place you could use a C7 chord, like, for example, as a diatonic chord in the key of F, you can also toss in a C13.*
Back, now, to our friend, the C13b5b9. The naming convention for chords goes like this: You start with a known chord, like C13, and then you add the stuff that doesn't fit after, like, for example, a b5 and a b9. That means, a C13b5b9, in all its glory, is spelled out like this:
C _ E _ Gb _ Bb _ Db _ F _ A
Now, that's too many notes to actually play (at once) on a (six string) guitar. Taking into account the physical limitations of the instrument, with the physical limitations of the human hand, you have to eliminate some notes, so that you can actually have a chord that you can play. Maybe surprisingly, maybe not, the first thing you often drop from voicings of larger chords, is the root. The hope is that you can either imply it, or that some other kindly member of the band will fill it in. The second choice is usually the 11th degree. There are several reasons, but the short version is, the 11th, which is also the 4th, often adds a kind of strange quality to chords. It's a fun thing to play with, but in a chord with a lot of peculiarities, you have to be careful which ones you include. The third is fairly low on the list of desirable cuts, because that note determines the major or minor quality of the chord. The b5 and b9 are probably best not to cut, if only because if you cut them, you change the basic nature of the chord (a C13b5b9 without its b5 is just a C13b9, and that's a different animal). Also, the b5 and b9 add the diminished quality (the first four notes of the chord are only two half-steps away from being a C diminished 7th chord) that makes the silliness from yesterday possible. The 13 is the note that makes the chord a 13, so, again, best to leave it. If you cut the 11 and the 13, you just have a C7b9b5 or something, and that's scarcely the same!
This leaves a chord that looks like this:
x _ E _ Gb _ Bb _ Dd _ x _ A
Why not just play that? Well, besides being kind of awkward on a guitar, it's frankly not as fun as playing around with inversions. Inversions? Inversions! That means you take those notes, and change the order to make them a)more interesting, b)fit the song better, or c)easier to play, because, let's face it, we're guitarists. We're lazy.
How could it b)fit the song better? Well, there are several ways. If you need a chromatic progression in the bassline, and are moving from an F to a C7, our friend is a fun choice, because the F moves up to the Gb, and the C7 becomes an entirely more fun C13b5b9 (did I mention?). Is that too busy for your song? Then don't use it. This is a special-case kind of chord.
Suppose you have a song with slow changes, say:
F - Gmin - C7 - C7 - F (a fairly standard jazzy progression, with each chord getting one measure)
If you want to make the chords more interesting than just sitting on a single chord, in place of the C7, Try this:
These are all chords that work as C7 chords (specifically, C7-C9/B-C7/Bb-C13-C7/G-C13b5b9), and it has two neat effects. It sets up ascending scale-wise motion on the top, with the highest notes being C, D, E, F, G and A, and it sets up mostly-chromatic motion on the bottom, C-B-Bb-A-G-Gb. It has that great droning E-Bb in the middle, holding the tritone at the center of the chord. The fingerings get a little tricky, but the end result can be worth it. That also puts you in a prime spot to resolve back to that F, with your stepwise motion down to a nice, easy, very standard voicing.
That's one more use for our new friend, the C13b5b9. It makes a neat passing chord when you have to stay on a C7, but you don't want to use just the same old C7.
Enjoy! Or, more likely, don't!
*OK, that's not always true, the opposite only usually is, but for the moment, we'll pretend that all songs could use extra jazz, and that anything that makes them more harmonically interesting will make them better. Again, just roll with it.