watchu gonna do about it?
| i'm a music theorist now. watchu gonna do about it? |
so, okay. conceptually. the reason we use 6 chords in the first place is simple. how do you voice a I chord after a V7 so that it actually sounds resolved. the reason why a V-I authentic cadence works is because of the voice leading of the 5 7 & 9 of the V chord going to the 5 1 & 10 respectively, and 5 1 10 (if you write it normally as 5 1 3) is in fact Imaj. if we try to apply this to a V7 chord we immediately run into a problem. the most intuitive way to add a fourth voice to a Imaj is to make it a Imaj7, however this Preserves The Leading Tone. so the primary thing that's driving the resolution of a V-I isn't actually Happening and in fact Remains Tense (the V7 has a 5 7 9 11, which resolve to the 5 7 8 10, keeping the 7). so, what to do? we can't raise the 7 in a Imaj7 because then it would become an 8 and we'd thus have a doubled voice, and a doubled voice is a wasted voice. we can however lower the 7 in a Imaj7 down to a b7 resulting in a I7 chord, which does indeed solve the half-step tension between the 7 and 1 at the expense of introducing a Tritone between the 3 and b7 (because alas that's the Whole Point of a dominant seventh chord). however, lowering it by two semitones gives us a very pleasing sound, a I6 chord. the 6 does clash with the 5 but it's a major second dissonance rather than a minor second dissonance between the 7 and 8, which is much less in-your-face.
unfortunately the humble 6 chord doesn't come without its drawbacks. although we got rid of the dissonance in a maj7 chord, dissonance isn't necessarily Motion (i.e. tension), it also functions as Color. by choosing a more consonant tone we've made the chord slightly more boring. this is why it's very common to add the 9th to the I6 chord, resulting in the one the only I69 chord. it even has a very elegant Quartal voicing as a stack of fourths!
great okay so here's the pitch we take a 6 chord and then add the 7th back
actually we don't even just add the 7th back we add a fucking b7 to make it a Dominant Seventh chord. so we go through the effort of using a 6th for its consonance and then also throw in a b7. which creates a tritone against the 3 again but also creates a minor second against the 6th. why a dominant seventh? because now it's a
why the fuck did i come up with this? well back in the mid old days when i covered Istanbul (Not Constantinople) i thought about also covering the instrumental and trying to cram the number 67 as many times as humanly possible into the composition (the other idea i had was to alternate between 6/8 and 7/8 because unfortunately the 6/7 time signature is not real), and as a quartal chord enjoyer the 69 chord popped into my head relatively quickly and i thought I Can Exploit This.
there's two ways of going about a 67 chord. one is the way i just mentioned, a major sixth and minor/dominant seventh. the other way is a major sixth and Major seventh. ultimately both have a minor second dissonance in them While Being Sixth Chords is chaos enough so for now i'll focus on the dominant type.
so they're a Bit too dissonant for a tonic chord in my personal opinion so i'll be talking about resolving a V67 to some kind of I chord. the notes in a V67 are the 5, 7, 9, 10, & 11. taking octave equivalency into account those are the 5, 7, 2, 3, & 4. there's just a big cluster of Stuff that's difficult to resolve anywhere satisfying. we can of course take the boring lame easy way out by going V67-V7-I6 but that's stupid and i refuse to do it.
the most intuitive way in my opinion to resolve it is into Imaj9#11no7 chord: 5 7 9 10 11 going to 5 8 9 10 #11 and thus acting as a 1 3 5 9 #11 kinda thing.
the reason this is the most intuitive way is because if you Don't try to spread the notes out across octaves there's a little bit of a problem with the 7 trying to resolve to a 1 or a 6, the 2 trying to resolve to a 1 or a 3, the 3 Existing, the 4 trying to resolve to a 3 or a 5, and the 5 Also Existing. this can be solved by removing the 3 that's really obviously in the middle of everything and fucking up the voice leading, but unfortunately this demotes our V67 chord to a V7 chord because that's where the 3 was coming from in the first place.
a less obvious way to solve this is to remove the 2, turning the chord from a V67 a a V67no5. this can be resolved into a Imaj9no7 (even more specifically the 4 resolves down to a 3, so you can use a suspended chord and resolve to Imaj9sus4no7 first), or, with a bit of creativity, directly into a I6 chord (5 7 3 4 to 6 1 3 5 respectively).
it's kind of funny how insanely simple it is