If you’ve ever wondered how a guitar tuner works, a recent post by forum user jpk unravels the mystery through a project in which they built their own DIY instrument tuner using a Teensy 3.6 and the Teensy audio library.

In the project, jpk uses fft frequency estimation and the Yin algorithm from the Teensy audio library to determine the accuracy of the incoming frequency in hertz. The device also includes a metronome so musicians can keep time, an LED indicator that responds to the note’s accuracy, and a display.The Teensy 3.6 version includes an LED indicator and display. A newer Teensy 4.0 version includes a speaker, rotary encoder, button, and lithium-ion battery charger. Jpk even made custom wood enclosures with transparent lids (so you can see the handiwork) to house both models. If you’d like to try it out yourself, jpk generously shared the project files to our forum.