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Deriving Keys from Chords in Music

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Re: Deriving Keys from Chords in Music

#4
This post shows that some very simplistic algorithms can’t unambiguously determine a key. But I don’t think it establishes that a more sophisticated algorithm could not. Key center is not just based on chords and notes in a scale. It’s based on the note/chord that seems like the place where the music is at rest, or at home. Many songs have non-diatonic chords, but it’s still fairly obvious what key they are in.

That said, there are examples where they key is ambiguous even to humans (e.g. Hey Joe [C G D A E], or Sweet Home Alabama [D C G] but disputed whether it’s in G or in D).

Re: Deriving Keys from Chords in Music

#5
post #4

This post shows that some very simplistic algorithms can’t unambiguously determine a key. But I don’t think it establishes that a more sophisticated algorithm could not. Key center is not just based on chords and notes in a scale. It’s based on the note/chord that seems like the place where the music is at rest, or at home. Many songs have non-diatonic chords, but it’s still fairly obvious what key they are in. That…

Yea, and it's possible to write chords such that it's actually ambiguous where the tonal center is. To some extent, every (successive diatonic) chord narrows it down, but it's possible that there simply isn't enough information to narrow it down to one key. Or they did something non diatonic to what was happening before, and you have to readjust.

Re: Deriving Keys from Chords in Music

#6
One useful heuristic (at least, the one I usually go to first if I'm not sure what key a song is in) is that root of the final chord of the song is often the same as the root of the key. I suppose that probably works better for some music traditions than others. Also I believe some songs in a minor key sometimes end by converting the root chord to major.

Re: Deriving Keys from Chords in Music

#7
post #4

This post shows that some very simplistic algorithms can’t unambiguously determine a key. But I don’t think it establishes that a more sophisticated algorithm could not. Key center is not just based on chords and notes in a scale. It’s based on the note/chord that seems like the place where the music is at rest, or at home. Many songs have non-diatonic chords, but it’s still fairly obvious what key they are in. That…

Yeah that definitely doesn't show algorithms are worse than humans.

Re: Deriving Keys from Chords in Music

#8
I am no musician. I heard quite a few musicians, with or without innate perfect pitch, can tell the keys in a chord, though maybe not to the 100% accuracy. For example, something like what the kid is doing in this video [1]. I am a bit surprised that this can't be done programmatically.

[1] https://www.youtube.com/watch?v=vXivZlPu0ms&t=175s

Re: Deriving Keys from Chords in Music

#10
post #8

I am no musician. I heard quite a few musicians, with or without innate perfect pitch, can tell the keys in a chord, though maybe not to the 100% accuracy. For example, something like what the kid is doing in this video [1]. I am a bit surprised that this can't be done programmatically. [1] https://www.youtube.com/watch?v=vXivZlPu0ms&t=175s

”Key” in this context refers to key signature rather than physical keys on a keyboard.
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