Unless you already considered yourself well-versed in the mathematics and science of sound, you'll face a rather steep learning curve when using Expression Tone Generator. Basically, this program lets you create sound effects based on mathematical equations you write using certain values such as sine, cosine, and tangent. The nonresizable interface is no beauty, but since this program only does one job, it's not too tough to find your way around. The application comes with a couple of preloaded equations as examples, but unless you're already knowledgeable in this field, you'll have to consult the help file to even have the slightest clue as to how to write one of your own. Still, the tool that shows you the notes of the scale and the frequency numbers did prove to be somewhat helpful to us, and we were eventually able to generate a couple of wild sound effects simply by trial and error. If you get a sound you really like, you can save it as a WAV file. Although it could benefit from a tutorial and more detailed help files, Expression Tone Generator might be a worthy download to musicians or folks involved in audio production, especially since it's free.