Yes, you can overdub on Track 1. It sounds like the DUB setting for Track 1 is set to 0, which means when you overdub on Track 1, it fully erases any previously recorded audio while it records new audio. To allow overdubbing on Track 1, do the following:
1. Ensure TRACK 1 is selected. Press the TRACK 1 button if it is not already lit.
2. If the LOOP/DUB LED is not lit, press the PAGE button until it is lit.
3. Press the VALUE knob once so that the dot to the right of the two right digits is lit. The two right digits represent the DUB or Overdub value.
4. Turn the VALUE knob to change the DUB value for Track 1. Set it to 10 so that you can overdub onto Track 1 without the previously recorded audio being erased or gradually lowered in volume.
5. Try overdubbing on Track 1 now. It should work like the other tracks.
