[ELECTRON] Idle speculation about music and compression files

[chris]

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Thanks a lot for this Gordon

This train of thought was started after ripping a few CDs without checking
the quality settings (they're set foolishly low in my default
installation). The high end parts of some gabba track (was Knifehandchop)
turned into the kind of mud you describe.

The other part I was thinking about was the way that dubstep (veryvery
heavy basslines) made absolutely no sense to me for the first couple of
years people were recommending it to me. It wasn't until I heard it live
through massive speakers that I was hearing everything that was there.
(Don't know if this caused by harmonics, or just the physical weight of the
sounds.)

Then there's some ultra minimal music that sounds different depending on
your position relative to the speakers (e.g. Sachiko M, Ryoji Ikeda) -
where do those sounds go? (If a mixing desk feeds back whilst unplugged,
does it make a sound? :p )

Then as an art-thought experiment: what about those sounds that I only
noticed through the uncompressed speaker stacks? Do they exist enough to
survive independently? If so, what would they sound like on their own?

Something like this? (in flac, naturally):
http://dl.dropbox.com/u/4218465/Sachiko%20M%20-%2001%20-%20YT.flac

Hey, anyone think the Arts Council will give us a grant to test all this? :p

chris h

Gordon JC Pearce wrote:
> On Fri, 2010-04-02 at 12:42 +0100, chris wrote:
> 
>> Does anyone have ideas about whether it would be possible to make a piece
>> of music that would be impossible to store digitally, compress as MP3, etc.?
>>
>> I have this foggy notion that the compression voodoo loses certain types of
>> sounds, at the top and bottom limits, and it's therefore feasible for a
>> tune (loosely defined ;p ) to completely disappear if that's where all of
>> its action is.
> 
> Most lossy compression uses perceptual effects to determine what can be
> thrown away - ie. if a particular frequency cannot be heard because it
> is masked by another, louder frequency nearby it will be discarded.
> 
> Now, as you increase the amount of compression, you become more ruthless
> about what you throw away - so the amount of detail remaining decreases
> and the reproduction is less accurate.  To see this at work, take a
> recording of some nice bright TR-808 hihats, and make several compressed
> copies of it at lower and lower bitrates.  You'll hear that at 320kbps
> it sounds almost unchanged, at 160kbps you have to compare it with the
> original to tell the difference, at 128kbps it will sound a bit
> "sizzly", at 96kbps there will be distinct "slurring" on the attack
> portion and at 16kbps it will sound like someone shovelling sand into a
> bucket.
> 
> Okay, so can we make a piece of programme material that would be
> destroyed by lossy compression?  Well, you could make something that was
> deliberately designed to put the information in the bands that would be
> dropped out - but the whole point of dropping bands out is that you
> wouldn't hear them anyway!  So the chances are that you'd only be able
> to do this if it was a piece of music intended for watching on an
> oscilloscope.
> 
> It's interesting to note that although simple AFSK data (like synth
> patch dumps recorded to tape) can be Ogg- or MP3-encoded and played back
> successfully, there are data modes that rely on phase-shift keying and
> the relationship between phases in a signal that are extremely badly
> affected by lossy compression.
> 
> Gordon MM0YEQ


- --
chris h

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