# Question on Tonal Harmony



## tdc

This question came to me when watching a video talking about jazz theory on youtube. The person said you can simplify how you see chords in relationship to each other by their function in relation to tonal harmony, in other words: 

In a major key the 1, 3 and 6 chords are equivalent to tonic chords
The 2, 4 are subdominant
The 5 and 7 are dominant

I then noticed in this video and others I came across they ignore talking about the same functions in minor keys? I wonder why? Do these chords function in the same way in relation to each other in minor keys?


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## Bwv 1080

IV, V and vii are the same in minor ( with a raised 7th). III and VI can also sub for tonic but also imply the relative major


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## EdwardBast

My (idiosyncratic?) views on these issues are that calling III and vi equivalent to or substitutes for tonic is an overstatement obscuring more than it elucidates. More important, the major and minor modes aren't examples of the same kind of phenomenon. The minor mode is a much more complex set of conventions and practices that doesn't readily reduce to a scale or a set of harmonic functions.


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## Woodduck

EdwardBast said:


> My (idiosyncratic?) views on these issues are that calling III and vi equivalent to or substitutes for tonic is an overstatement obscuring more than it elucidates. More important, the major and minor modes aren't examples of the same kind of phenomenon. The minor mode is a much more complex set of conventions and practices that doesn't readily reduce to a scale or a set of harmonic functions.


Not idiosyncratic, but shared with at least one other.


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## Bwv 1080

There is a difference here I think between jazz (which the op was referring to) and classical - with the 7th chord being the smallest unit of harmony in jazz, it easier to hear III as part of the tonic minor 7th chord. Comping in Jazz, one would not think twice about playing III where the changes indicated the tonic, whereas in classical it usually implies a change of mode


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## BrahmsWasAGreatMelodist

In terms of the local stability / harmonic force implied by these chords it's largely the same:

"Tonic": i, III, VI
"Subdominant": ii, iv
Dominant: V, vii (dim)
'
But I agree with EB and Woodduck; this classification is not very useful.

^^^
The post above is also good. Think about the nature of triadic harmony, and how this leads to VI, I, and III sharing common tones. When you allow for extended harmony as in jazz, it's only natural that these serve tonic functions.


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## Roger Knox

Woodduck said:


> Not idiosyncratic, but shared with at least one other.


I learned the basics of classical harmony and jazz harmony at distinctly different times. When done that way, and thoroughly, you can later make the interesting comparisons between the two yourself as the need arises. From a teaching perspective, I don't like the idea of making back-and-forth parallels between classical and jazz harmony from the beginning. The basics in these areas first have to be "overlearned," applied in practice without confusion till they become second nature.


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