The DR-3 contains a metronome that is normally used to follow along with when programming your own User Styles. It can also be used as just a stand-alone metronome as well.
Here's how to activate it:
1. Turn on the DR-3.
2. Turn the VALUE dial to choose "U001" - (or any blank User Style number above U001).
3. Press the TEMPO/TAP button, and then turn the VALUE dial to set the desired tempo.
4. Press the STEP REC button.
5. Press START (>/||) - (Not the INTRO/START button). The metronome will start. Make sure you have headphones connected to the DR-3's PHONES jack or the outputs connected to an external amp/PA/mixer.
6. Press STOP when you're finished.