I am in need of a free tone generator (enter a frequency to output) for Mac OS X that can be "dialed" in real time. I need to be able to adjust a slider without having to stop/start/type in a new value. I have not been able to find a single application that can do this.
Here's a tone generator / tuner application that I wrote, available for free online:
It was originally to help people with tinnitus find the frequency their ears are ringing at, but it certainly has other uses.
Audio Signal Generator by Bill Farmer, GPLv2 licensed.
It doesn't have a "slider" per se, but its knob dial might just be enough.
If you want something more complete and don't mind parting 5 USD, AudioTest from Katsura Shareware is also very usable, with a slider.