Mobile phones have quickly evolved from communication devices into miniature computers, and have also partially replaced other devices: the watch, the camera, the flashlight… Previously, tuning a guitar required one of the following: a pitch pipe, a nearby piano, a very good ear, or the classic standalone electronic tuner.

Now, we have mobile phone apps like GuitarTuna. When a string is played, GuitarTuna uses the phone's mic to measure the string's vibrational frequency, or pitch. It then gives real-time feedback on the screen as the string tension is adjusted, showing the current pitch next to the target pitch. With the ubiquitous smart phone, it's easier than ever to keep the guitar in tune!