This is a wrapper to Sox the Sound Exchanger http://sox.sourceforge.net/ which lets you play, write, read and convert audio signals in various formats, resolutions, and numbers of channels.
The functions call sox commands via the shell,
that is, the
play executables must be installed
and in the path to the executables must be set.
In the past this was part of the synthesizer package.
There is some ancient code, which allows interactive playback using the shell-pipe package on GHC-6.2, where no runInteractiveProcess was available.