TuningFork is an open source Swift sound processing library by Comyar Zaheri that simplifies the detection of pitch, frequency, and amplitude of audio.
Tuningfork works directly on microphone input so you can easily create apps that require pitch detection such as tuning apps.
Partita is an example open source instrument tuner app that utilizes tuning fork with a nice interface.
Here is an image showing Partita in action:
You can find the TuningFork sound processing library on Github here.
You can find the Partita instrument tuner source code on Github here.
An easy to use sound processing library great for tuning apps.