This program allows you to record the output of any standard OSS
program (one that uses /dev/dsp for sound) without having to modify or
recompile the program.  It uses the same idea as the esddsp wrapper
from the Enlightened Sound Daemon (in fact, vsound is based on
esddsp).  That is, it preloads a library that intercepts calls to open
/dev/dsp, and instead returns a handle to a normal file.  It also
intercepts ioctl's on that file handle and logs them, to help convert
the audio data from its raw form.  Vsound then uses sox to convert the
raw data to the desired file format.

The upshoot of this is that instead of playing sound to the sound card
in your computer, the data is recorded to a file.  This is similar to
if you connected a loopback cable to the line in and line out jacks on
your sound card, but no DA or AD conversions take place, so quality is
not lost.

WWW: http://www.zorg.org/vsound/