I have a SB Live! sound card in my PC which comes with software capable of several nice audio effects.
I’ve been using it to slow down tunes without changing the pitch for quite a while now… very handy for learning faster tunes.
Lately though, I’ve been playing with the pitch shifter effect.
I’ve learned that you can raise or lower the pitch of most whistles by several notes without any significant loss of sound quality.
I just thought I’d pass that on to anyone who might find it useful in their recording work… or who just might think it’s cool. 
I’d also be curious to hear from anyone with a professional grade pitch shifter as to whether such a device can surpass the quality of a SB Live! or not.