NCH Tone Generator is software that generates a sustained tone at a frequency you designate. The tone can be a sine wave, a square wave, and a number of other basic waveforms. Tones can be designates and saved to a list. Playback is with a click on the saved item. One use would be to setup a just scale and match chanter tuning against that. It’s also a useful reference for drone and regulator tuning. PC Only.