From the factory, the RC-300 is set to "Multi-Mode" which lets you play all three tracks in a memory location simultaneously. If you want the tracks to only play one at a time, choose "Single Track Play" for the play mode. For example, Single Track mode would work well for a looping setup where you'd have the first track as the Verse, the second track as a Bridge, and the third track for the Chorus.
Here's how to turn on Single Track Play.
1. Choose a memory location to edit.
2. Press the MEMORY EDIT button.
3. Press the ( >) button to choose "Single Tr Play."
4. Turn the MEMORY/VALUE knob to choose "ON."
5. Press WRITE twice to store the new setting to the memory.