Audio Narrowband Filter

This app implements a audio filter around any selected pitch. The sound from the microphone is filtered and sent to a headset. The app features:
* Adjustable bandwidth from 400 cents to 50 cents
* Synthesized beat rates that can be switched on for beat rate recognition training.
* Piano keyboard selection of the selected pitch
* Spectrum analyzer display of the input sound
* All functions explained through self-contained help document