Korg DTR2000 Pro Rack Mount Multi-Mode Auto Chromatic Tuner Chromatic, guitar (6-string, 7-string)/bass, and open modes. Five types of open tuning. Three types of display: cents, hertz, or strobe. Seven-semitone flat tuning mode supports dropped tunings up to 7 semitones  a worldwide first. Adjustable calibration of 438445 Hz. (Select either manual or auto)