What determines the function of a chord?

YoungCapone

New member
I’ve been trying to learn about functional harmony and I keep asking myself the above question. Each chord seems to have a general function (with exceptions) within scales, but why is that so? Were scales made with those functions in mind, or were those functions agreed upon or discovered after scales were already determined? Is it a result of having 7 notes in a scale? For example, if you were to choose 7 random notes within an octave...would the 5th chord always serve a dominant function?

DISCLAIMER: I know I’m asking a simple question that doesn’t have a simple answer and I don’t expect any response to be cut and dry. I also realize I’m making a lot of assumptions about the way music works that may or may not be true, however any insight at all would be helpful! Thanks!

 
lol - it is indeed a simple question with a complex answer!

However, I'm just going to give a few points here.

One important thing to remember is that we're talking diatonic western music here... Other cultures often have very different perceptions of chords and harmonic function.

One of the main drivers of diatonic music is frequency ratios. A perfect fifth, for example has a frequency ratio of 3:2. In general, the simpler the ratio, the "cleaner" the sound, which is why a perfect 5th is clean, but a major 7th is not (50:27, depending on... see below..). Chords which include notes that have simple relationships to the tonic note "fit" in the key easily, whereas chords with notes that don't have simple relationships "don't fit".

Now... Almost all the music we hear and produce is actually "even tempered", which muddies the waters of those frequency relationships. The reason for this is that if you tuned a piano so that E to A is exactly 3:2, your perfect 5th would only work in the key of A, and other keys would be way off by the time you tried to do 3:2 tuning for all 5ths. You can't. So, even tempered tuning is an accepted compromise so that harmonies sound more or less the same irrespective of what key you play it in.

Another point is cultural track record. i.e. chords have certain functions because people have used them that way for centuries, and we're used to hearing them. Following a dominant 7th chord with a return to the tonic is so deeply rooted that we get a certain satisfaction from hearing it; and composers use it for that effect. The relationship between a major key and its relative minor (both have the same key signature) is so well-plumbed that it's another instance of commonly-perceived experience that composers use.

That's all for now - my wife's summoning me. :) Hope this helps!
 
Foxcorner— Thank you for having the patience and taking the time to post a well-reasoned response. I was hoping someone exactly like you would show up. Welcome, by the way!


GJ
 
The scale of the key signature determines the function of the chord.

Also the tonic determines the chord function and interval.

Check out this basic music theory tutorial and the scale app from Sound Gunz

 
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