[linux-audio-user] Green's Function in Audio --- Demo Song

davidrclark at earthlink.net davidrclark at earthlink.net
Sat Aug 14 02:44:25 EDT 2004

Hello everyone.

Rather than participate in the recent interesting discussions, I decided
to record/process a song and fix my software, especially since my favorite
window manager is none at all.  I prefer running scripts while having a beer 
then taking a nap or watching a tape of Joe Shmoe 2.  (I've never cried
so much from laughing, but I'm easily amused.)

And rather than another demo, I decided to post a complete song which utilizes
the Green's function technique I have mentioned previously.  I'd like to
say that this song was created exclusively with Linux, or perhaps more
appropriately, GNU audio software, but I used Windows sequencers.  I used
my own command-line software to process the mix, created from monophonic
recordings of each musical part or sub-part.  I then applied JAMin to
the final mix, using another piece of my own software, jackd, and 
qarecord to capture the result.  I then downsampled it with my own
overlapping FFT program, then used lame to produce the mp3 file.
I think that's all, but I could easily have left something out.  As a 
matter of fact, I had to fix some bug in my stuff with "head --bytes=...."



For the person who may have read the Green's function notes without falling

The Green's function technique that was used was for a *point* source in
three dimensions in a very large room (~12,000 m^3) except for the overhead 
kick drum for which I used a *volumetric* source.  In the simulated concert 
hall, the overhead location is very close to the center of the room in one 
axis, so the timing for echoes is bad.  Using the volumetric source diffuses
this effect a little, just as rough surfaces diffuse sound in a concert hall
(otherwise you'd hear it in a concert hall, also).  This concert hall has
about 3 billion modes and they're all represented.


Regarding the piece itself, I've noticed that people like to comment
about the actual music.  Well, this is intended to be a demo, so it's
"very-high-quality elevator music."  The sound sources are a Korg N264
and a Roland XV-3080.  My focus is on the mathematical physics first,
then on the application (reverb, stereo separation, echo, filtering, etc.),
then on the music --- until it's finished.  Then I like to just listen....
This is the only area that I've ever worked in where I am my own 
customer, and it's really nice to have it that way.  Damn nice.
Thanks very much to the developers of GNU software, the Linux kernel
people, and the developers of JAMin, jackd, qarecord, and lame.  And
a special thanks to the developer of the "head --bytes=..." utility.

Regards to all,

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