Altered and Enharmonic Modulation

Page 1

music theory for musicians and normal people by toby w. rush

Altered and Enharmonic Modulation w œ œ ww œœ œ œ œ & b œœ

n œœ

œ

F: I

IV

V C: I

V

Altered common chord modulation is easy: remember diatonic common chord modulation, where we used a chord that was diatonic in both the old and new keys?

I

& b œœœ

altered common chord modulation is the same thing, only using the pivot chord as an altered chord in either the old key, the new key, or both.

F: I

œœ œ

IV

œœ œ

V E: b VI

# n www

# n # œœœ V

I

Now, in both diatonic modulation and altered modulation, we have one chord that plays two different roles, one for each key. But the chord type doesn’t change... if it was a major chord in the old key, it’s still a major chord in the new key.

...but what if the chord type did change? this technique is so — well, odd — that there are only two specific ways to do it.

in enharmonic modulation, we respell a chord enharmonically so the chord type itself is different in the old and new keys.

beethoven did!

D b : V7

C: Ger.6

we can take advantage of this and use it as a pivot chord... where it acts like a german augmented sixth in one key but like a V7 (or a V7/x secondary dominant) in the other key!

&

bbbb

b œœ

? bb b œ bb œ

œœ n œ nœ

D b : IV

6

œœ

œœ n œ n œœ nœ 7

V C: Ger.6

V

I

note that the pivot chord above is approached like a dominant seventh, but resolved like an augmented sixth chord!

&

b b wwww

7

&

b b wwww

a°56

respell

&

b bb wwww

b b # wwww

fully diminished seventh chords are cool for a lot of reasons, and one of them is that they are equidistant chords: inverting a fully diminshed seventh yields another root-position fully dimished seventh chord. invert

ever notice that the german augmented sixth chord is just like a major-minor seventh chord with the seventh respelled enharmonically?

&

b b ∫ wwww

c°7

meaning that a fully diminished leading tone seventh chord can be a pivot chord into three other possible keys:

# œ & œœ G: I

# œ & œœ G: I

# œ & œœ G: I

b œœœ œ

which can be respelled as

vii°7

b œœœ œ

vii°7 E: vii°65

which can be respelled as

vii°7

b œœœ œ

# œœœ œ

œ b ∫ œœœ

vii°7 b D : vii°34 which can be respelled as

vii°7

licensed under a creative commons BY-NC-ND license - visit tobyrush.com for more

œ b œœœ

vii°7 b B : vii°42

# œœœ I

n b b œœœ I

b n œœœ I


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