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PostPosted: Wed Mar 27, 2019 9:20 am 

Joined: Mon Mar 18, 2019 6:20 am
Posts: 3
"Would like to know a little bit about the mechanism?

Check it Out: https://www.guitaa.com/chords/jayda-happy-for-you-official-music-video

Select any song, It'll extract the chords. But How?"

PostPosted: Wed Mar 27, 2019 12:29 pm 

Joined: Fri Mar 03, 2006 7:09 pm
Posts: 6237
Location: Hegins, Pa
looks interesting
do you know anything about this site? I gave it a quick looksee.

John Hall
Blues Creek Guitars Inc
Authorized CF Martin Repair Center
president of Association of Stringed Instrument Artisans

PostPosted: Thu Mar 28, 2019 8:47 am 

Joined: Mon Sep 03, 2018 6:01 pm
Posts: 22
music143 wrote:
Select any song, It'll extract the chords. But How?

If it's anything like RiffStation (software I bought a few years ago, sadly no longer available) then it's basically a polyphonic equivalent of the pitch detection in electronic guitar tuners, coupled with some heuristics to help guide the algorithm.

I've not used the site you've linked, but RiffStation does a pretty good of identifying chords in simple songs that don't stray beyond the I IV V + relative minors - but doesn't cope well with key changes, modulations and songs that use both minor and major versions of the same chord.

PostPosted: Fri Mar 29, 2019 9:18 am 

Joined: Wed Aug 13, 2014 12:14 pm
Posts: 1340
I don't know if this is what it does, but one way of doing it would be to do a Fourier transform of the sound wave, which would give you the individual frequencies that add together to produce the sound you hear. For example, a C chord is made up of a 261.63 Hz wave (C), a 326.63 Hz wave (E). and a 392.00 Hz wave (G). If the output of the Fourier transform was those three frequencies, you would know you have a C chord.

Now, what that program does is considerably messier than that. The melody is constantly changing, so it must do a sample every x milliseconds, for some x. At any instant, the chord may be incomplete or ambiguous. Somehow or other it has to average all that out and get some sort of general trend, which becomes a "best guess" for a chord.

Don't believe everything you know.
Anything is possible if you don't know what you are talking about.
When things are bad, try not to make them any worse, because it is quite likely they are bad enough already. - French Foreign Legion

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