Pass path to thttpd for CGI

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I sort of have this working but not quite. I have 
http://mysite.com/music/play/song.mp3 and this plays fine in the browser 
by accessing the mp3 file in its folder. However, I want to handle 
requests to download the song at 
http://mysite.com/music/download/song.mp3 with a CGI script that has no 
extension (it's C). I can get /music/download to be handled by CGI in 
thttpd but I don't know how to handle the changing song titles cause 
everything I've tried fails.

location /music {
     try_files $uri.html $uri/index.html @music;
}

location @music {
     proxy_pass http://127.0.0.1:8000;
}

In thttpd.conf I have:
host=127.0.0.1
port=8000
dir=/www/cgi-bin
cgipat=/**

And inside the cgi-bin is a standalone program called "download" so 
/music/download returns a web page generated by that executable  just to 
test this. I've tried so many variations including rewrite that I've 
gotten myself pretty turned around as to what I should be doing.
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