music editing / decomposition

Daniel Joyce daniel.a.joyce at worldnet.att.net
Thu Sep 18 19:18:21 UTC 2003


On Thursday 18 September 2003 11:40, Gary McGovern wrote:
> Thanks for all those links and resources. I'm more than surprised this
> isn't more evolved. I thought if the human ear could selectively pick out a
> track in a composition / song then that track has its own unique state and
> behavior and it would just be a matter of defining the state and behavior
> and identifying those tracks electronically.
>
> Thanks again.
>
> Gary
>

The problem is, music is the sum of all the frequency, harmonics, and phase 
information in it.

If I give you the number 100, can you tell what numbers I summed or multiplied 
to arrive at that number? 100x1? 20x5? 4x20+20? It's impossible to tell, the 
information is lost in the process. :)

Now with music, that isn't entirely true. But, yer gonna need to do some work. 
You're probably going to need to work in the Frequency domain ( so use a FFT, 
or wavelet transform to get there ), and also, phase information ( a bit more 
trickier ). Once you've got all that, it might be possible ( depending on 
signal noise, etc ) to pick out one trumpet, and 'follow' it through the 
piece. You KNOW what a trumpet sounds like, but how do you tell the computer 
that? ( Possibly, take a trumpet sample, and have it scan for a 'closest' 
match in some fashion ).

Turns out, the reason why it's easy for people to do it, to hear and follow 
the trumpet piece in the symphony, is that some of the work is done by the 
structure of the inner ear ( Different frequencies excite different areas of 
the spiral shaped inner ear, so in essence, it's performing a Fourier 
transform ), and the brain is a massively parallel machine. 


The Meek shall inherit the Earth,
for the Brave are among the Stars!



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