Strobalizer

The revolutionary free optical guitar and bass tuner that actually works. No need to plug in - just point and tune!

To use the Strobalizer as a guitar tuner, select a string on the screen, hold the phone with your plucking hand pointing the torch at the string and pluck with the thumb. The string will oscillate very slowly under the light of the Strobalizer - adjust tuning until the string stops moving entirely. If the string moves more quickly you need to tune in the other direction. Keep replucking occasionally to keep the string alive, as with any other tuner.

For tuning bass, use the same procedure but select a string from the left hand column.