[om2]

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).

[frogulis]

Adam Neely released a pretty in-depth video recently with the opinion that Hey Joe is straight-forwardly in the key of E, as long as you don't get stuck trying to fit it into a diatonic, traditional Western framework. It's a good watch.

https://www.youtube.com/watch?v=DVvmALPu5TU

I had an unanswered question after the video -- are there listeners who don't feel that sense of "home" when arriving at the E chord? I certainly do feel "at home" on the E, but I'd be curious to hear others' opinions.

[RHSman2]

I’ve played it a fairly large amount in bands. First time I have heard that it’s in the key of E. Totally makes sense to me especially in the Hendrix version with the semi chromatic bass walk to E.

[lc9er]

I think context is important. If you are talking about guitar based music, then E is a pretty safe bet as home. But what if a group doesn’t use standard tuning? The first two examples that come to mind are Alice In Chains and Tool. They use E flat tuning and drop-d tuning, respectively (mostly). When I listen to them, Eb and D are home.

[coldtea]

The instrument tuning doesn't change the fact that a song has a key/home.

If someone plays it in another key, transposes it etc, it will still have a specific key, just transposed.

In this case of course it's about the Jimi Hendrix recorded cover version, not trying to get some key that would hold across all possible versions.

[ragona]

It feels like home because of the key of the song, not the instrument. Sometimes the guitar is tuned to play a song where the key matches the lowest string, but many songs are of course played in other keys.

[dkdbejwi383]

Jimi played in Eb a lot too. Kurt Cobain and SRV too.

[RHSman2]

That’s cos it sounds heavier but the key is relative.

[Glorbutron]

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.

[neolog]

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