Data via Bluetooth to a Raspberry PI 3 board - C program needs to be implemented for the Raspberry to handle the incoming data stream, detect frequency values in Hz

I am looking for a freelancer to complete a small project involving an Android app to send data via Bluetooth to a Raspberry PI 3 board. The android app is already existing (might need some adjustments) and is able to send the required data (microphone audio data as float values) to the board, however a working C program needs to be implemented for the Raspberry to handle the incoming data stream, detect frequency values in Hz (e.g. using the FFT aka pitch tracking) and print it continuously to the screen. The project can be used to tune a musical instrument for example a guitar.