hey, welcome to 12tone!
back when I was in college, I think around theory 4, we got an assignment to write a
32-bar jazz song.
the specifics were left up to us, with one exception: the verse had to be in the key
of D major, and the bridge had to be in Ab.
now, if you've never actually tried to do that it may not be clear why it would be so
hard, but as the class's unofficial resident theory tutor I wound up getting a lot of questions
that week, so let's talk about why.
we actually already did a video on the basic techniques of key changes, or modulation,
but to review, they tend to come in one of two forms.
the first, direct modulation, is pretty straightforward: you just start playing in one key (bang) and
once your audience has absorbed that sound, you suddenly switch to a new one.
(bang) it builds energy, and it's a staple of pop and rock music, but a jazz song requires
something a little more subtle, and that's where the second technique comes in.
this is called a pivot modulation, and it works by using a chord that exists in both
keys in order to cover up the transition.
for instance, if we're playing in D major and we want to switch to E major, we just
have to find a chord they have in common, like F# minor.
(bang) this is the III chord in D and the II chord in E, so it's helps us pivot between
them.
I also snuck in an A major here, which is another shared chord and helps make things
even smoother, and by the time we land on that E major chord, it's hard to believe that
D ever felt like the root.
but we're not trying to pivot to E here.
we're trying to go to Ab, a tritone away from our starting key, and that makes shared chords
harder to find.
here's a complete list of all our options...
yeah, it's empty: the two keys have exactly zero chords in common.
but a direct modulation would sound really jarring, so what are we gonna do?
well, there's a couple options.
the first is to simplify.
sure, there's no chords in common, but the two keys do share a couple notes.
specifically, they both have G, and they both have this note, although they call it different
things.
if we drop the harmony for a second and just sit on one of those shared notes (bang) we
can at least start to smooth it out.
this is called a pivot tone modulation, and it works a lot like a pivot chord, but without
the supporting harmony it's not quite as clear, and you have to sit on it for a long time
to really make the transition work.
but let's say we want to keep playing full chords.
in that case, the first place to look would be modal interchange.
this is where you borrow chords from another scale.
for instance, the key of D major has no chord in common with Bb major, so we can't really
pivot between them.
but D minor has plenty.
in fact, D minor, the chord, is in both keys, so we can just borrow it as our pivot (bang)
and get a pretty smooth sound.
of course, using chords from outside the key is, itself, attention-grabbing, so if you're
planning to do something like this, it helps to use the chord a couple times in a more
normal context first, so by the time you get to the key change your audience is used to
the sound.
but this still doesn't help: not only do D and Ab major not have any chords in common,
they're so far apart that they don't even overlap with each other's minor versions.
but the idea of using chords from outside the key has merit, so let's try another common
borrowed chord, the secondary dominant.
this is a dominant 7th chord that points somewhere other than the root of the key, and we can
use it to help cover up some of our differing chords.
like, if we wanted to go from D to B, we could use a B7.
this points us to some kind of E chord, but whether it's the E minor in D or the E major
in B isn't clear until we actually resolve.
(bang)
but that's still not enough.
this lets us ignore the quality of our target chord, but we still need to find a shared
root, and D and Ab don't have very many of those.
could we use a D7 to resolve to a G chord?
well, in D, that works great: it goes to the IV chord, G major.
(bang) but how about in Ab?
well, that's a bit harder.
Ab does have a G chord, but, well, listen to it.
(bang) yeah, it's a diminished triad, and you can't really resolve to one of those.
it's not stable enough.
the only other shared note is C#, and that's a diminished triad in D.
but we're getting really close.
we just need one more tool, the tritone substitution.
we've covered this before, but basically it's just a dominant 7th chord resolving down a
half-step.
(bang) and this is perfect: in D major, the dominant 7th chord is an A7 which, conveniently,
sits a half step above Ab.
this means that it can resolve to either of our keys (bang) and finally we've got an answer.
this is what most of my classmates did and, in hindsight, considering we'd just learned
about tritone subs a couple weeks before the assignment, it's probably what we were supposed
to do.
but it's not what I did.
I decided to get fancy, and used a technique called a modulation chain, which is pretty
much what it sounds like: changing keys multiple times in a row.
I started by moving from D major to D minor.
this is what's called a parallel modulation, where you switch scales but keep the same
root.
then I went to F major.
this is a relative modulation, and it works because the two keys have all the same notes,
they just use them differently, so it's like an extremely subtle pivot. from there, I did
another parallel modulation to F minor, and finally one more relative modulation took
me to my ultimate target, Ab.
if you'd like to hear what that sounds like, I made a bonus video of it.
there's a link in the description.
but there's one more solution, one I wouldn't learn about for almost another year: the diminished
7th.
this is a fairly standard substitute for the dominant 7th, but with one twist: it's symmetrical.
let's look at C# diminished 7 (bang) the notes are C#, E, G, and Bb.
now if we go to E diminished 7 (bang) we've got E, G, Bb, and Db, which is another name
for C#.
it's the exact same set of notes.
because of this, the root of a diminished chord is always a little ambiguous, and can
change at a moment's notice, so we could play a C# diminished 7, implying a resolution to
D, but then suddenly switch to a G diminished 7 and resolve to Ab instead.
it can also resolve to F (bang) or to B (bang) giving us four possible targets for just one
chord.
but it goes further, thanks to the secondary dominant concept we talked about earlier.
say we wanted to go from D major to Db major.
that's also a pretty hard modulation, but the diminished 7th has our back.
we just need to hit C# diminished 7 (bang) then pretend it's a G chord and resolve it
to Ab.
(bang) normally, that'd be the end of it, but it doesn't have to be: if our G diminished
7 was a secondary dominant, then the Ab could be the new V chord instead, which would then
resolve to Db, completing our modulation. in fact, any diminished 7th chord can resolve
to either the I, the IV, or the V in any key, making it like a swiss army knife for pivot
modulations.
it can go anywhere it wants, whenever it wants.
no questions asked.
so yeah.
distant modulations can seem daunting, but there's plenty of ways to make them work.
do you have a favorite technique for making those difficult transitions?
let me know in the comments.
we're gonna be taking a couple weeks off for the holidays, but we'll be back at the beginning
of January, and we've got some pretty exciting plans for the new year.
until then, thanks for watching!
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