hey, welcome to 12tone building blocks, our monthly series about the fundamentals of music
theory!
last time we touched on the idea chord functions, or specific jobs that different chords in
a key take on, but the comments indicated that I may have brushed by those a little
too quickly, so this time I'd like to slow down and take a good, long look at exactly
how these functions work.
as a refresher, we break chords in a key into three main groups: tonic function chords,
dominant function chords, and subdominant function chords.
tonic function chords are the ones that provide a sense of rest.
they're calm, they're stable, and they don't take a lot of mental energy to process.
unsurprisingly, the primary tonic function chord is the I chord, built on the scale's
root.
it's like the home base of the key, and it's the strongest sense of rest you can find.
but it's not the only one: tonic function also includes the VImi and, usually, the IIImi,
each of which is only a single note away from the I chord.
this is especially obvious if we use seventh chords: the VImi7 includes all the notes of
the I major triad, and the Ima7 has the IIImi triad inside it.
they're all very closely related sounds.
another thing to note here is that all the tonic function chords share one note in common:
the third degree of the scale. which is kind of weird if you think about it.
I mean, you'd expect the most important note to be the root, wouldn't you?
but the third degree plays a critical role in defining what's called the modality of
the scale, which is what gives the scale its overall color.
without the third degree, you get ambiguity: it's not clear whether it's major or minor,
and that, it would appear, is a large part of what gives tonic function its strong sense
of rest.
the next chord function is dominant function: these are like an arrow pointing you back
home.
they're very unstable, and that creates a lot of tension that gets released when they
resolve back to a tonic chord.
the most common dominant function chord is the V chord, often played as an appropriately
named dominant seventh.
you'll also sometimes see the VII diminished or VIImi7b5, and all these chords have two
notes in common: the seventh degree of the scale and the second.
these encircle the root, and they both want to collapse in toward it.
the seventh degree's pull is especially strong because it's only a half step away, and that
strength has earned it the nickname "the leading tone" in music theory circles.
dominant chords also frequently feature the fourth degree, which is a half step above
the third.
as we mentioned earlier, the third is also a huge part of tonic function's overwhelming
consonance, so this downward resolution creates another strong sense of release.
even more powerful is the relationship between the seventh and fourth: they're a tritone
apart, which is itself a very unstable interval that would want to collapse even if it weren't
for the specific functions of its component notes.
and finally, there's subdominant function.
if you've been keeping track, you may have noticed that the only chords we haven't mentioned
yet are the IV and the IImi.
they're sort of a bridge between the other two groups: they take you away from tonic
function but they don't point you back yet.
they're also unstable, but, unlike dominant function, that instability comes almost entirely
from their relation to the key.
there's two notes that these chords both share: the 4th degree of the scale and the 6th.
most of the work here is done by the 4th, though: it sits above the third, just like
in dominant function, and disrupts the sense of rest that note provides.
it introduces ambiguity, and that creates tension, but it lacks the leading tone so
it's not quite so directional.
an interesting thing about subdominant function is that how its chords feel changes depending
on whether you're using triads or seventh chords.
the IV major triad contains the root of the key, which gives it a little extra grounding
to help set it apart from dominant function, whereas the II minor triad feels more adrift.
the IImi7, though, picks the root up itself, making it more grounded, while the IVma7 adds
the third degree, making it almost too stable to really serve as a subdominant chord. of
course, they both work either way, but which one is best depends on how many notes you're
planning to use, and I think that's really cool.
and that's chord functions.
hopefully this cleared up a couple questions, but before we go, here's a really simple rule
of thumb for identifying them: you just have to look for the third, fourth, and seventh
degrees of the scale.
if a chord has the third but not the fourth, it's gonna sound consonant and at rest, and
thus tonic.
if it's got the fourth but not the seventh, it'll be unstable and ungrounded, making it
subdominant.
if it's got the seventh but not the third, it'll be dissonant and directional, making
it dominant.
of course, that doesn't take into account chords that aren't in the key themselves,
but that's a topic for another time.
until then, thanks for watching!
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