Korpa 
Korg Pitchjack Plug-In tuner GB-1 BK
The Korg pitchjack is a guitar tuner that plugs directly into a guitar or bass instrument jack. The pitchjack tuner offers the features most sought after by gigging musicians, including a flat tuning mode for tuning as many as 7 semitones below standard pitch, and the ability to accurately tune 7-string guitars and 6-string basses.
The Korg pitchjack provides quick, accurate tuning virtually anywhere. The adjustable viewing angle of the pitchjack tuner's display can accommodate different guitar body shapes plus the angle and location of your bass or guitars jack.
The pitchjack has a compact folding design and accepts a key ring to easily attach it to your gig bag, case, or keychain. The Korg pitchjack tuner's built-in LED flashlight provides illumination as needed onstage or in other dimly lit situations.
