SweepGen turns a PC into an Audio Oscillator and Sweep Generator which can be used for testing audio or educational purposes. In conjunction with audio test instruments, you can make frequency response plots.
SweepGen uses the sound card in your PC to produce sinewaves that are mathematically correct almost to CD quality, indeed its more likely that the quality of your PC sound card will be the limiting factor rather than the code in SweepGen.

The license of this software is Freeware, you can free download and free use this music mixer software.