Mark, there are several. Here is one:
Quoting Mark Erbaugh <firstname.lastname@example.org>:
> As I continue my work on my own custom Pegasus control software, I have
> incorporated the ability to play .WAV files through the aux input. This
> allow me to use the computer as a digital voice keyer.
> However, I think that I can take advantage of some sound processing
> on the computer to customize the .WAV file to give it more punch. Other
> doing some dynamic limiting to increase the average power, are there
> that can be done to increase the chances of standing out or at least
> heard in a pileup? Is there a model of HF propagation that can be used
> experiment with the effects of various enahancements?