In the GT-100, you can choose whether or not you want to hear your guitar while tuning. If the Tuner is set to "Bypass," your guitar signal will be heard. If the Tuner is set to "Mute," the guitar signal will be muted. 

Here's how to set the desired Tuner Mode in the GT-100: 

1. Press numbered pedal's 1 and 2 simultaneously to activate the Tuner. 

2. Turn Knob #4 to choose the desired preference (MUTE/BYPASS). 

3. Press EXIT, or press pedals 1 and 2 simultaneously when you're finished. The new setting is saved automatically.