The Chromatic switch in the GTR-MIDI section of the GR-55 determines whether notes that are transmitted through MIDI will be sent chromatically, or whether the notes will include "bend" messages. Setting the Chromatic Switch to "ON" is usually recommended for instruments like Piano, since you most likely wouldn't want to hear piano notes "bending" from one note to the other.
Here's how to access and set the GTR-MIDI Chromatic switch in the GR-55.
1. Press EDIT.
2. Press the PAGE right button until you select the "SYSTEM" tab.
3. Press the cursor left /right buttons (or turn the dial) to select the MIDI/USB icon, and then press ENTER.
4. Press PAGE right to choose the "GUITAR-MIDI" tab.
5. Press the cursor up/down buttons to highlight "CHROMATIC."
6. Turn the dial to choose the desired setting - ON or OFF.
7. Press EXIT when you're finished. The new setting is saved automatically.