Boss DD-8 Reference Manual page 13

Using the LOOP (Overdubbing) Function
With the LOOP function, you can record up to 40 seconds of your
performance, and then have that content played back repeatedly.
You can also layer this as you perform something else, then record
these together (overdub).
1. Select LOOP.
Set the MODE knob to LOOP (the CHECK indicator goes out).
2. Begin recording.
Recording starts when you press the pedal switch (the CHECK
indicator flashes red).
* The maximum recording time is 20 seconds for stereo input or
40 seconds for mono input.
* Recording continues even if you release the pedal switch.
3. Stop recording0start playback.
When in the recording state, press the pedal switch to stop
recording and transition to playback (the CHECK indicator is
lit green).
4. Start overdubbing.
When in the playback state, press the pedal switch to start
overdubbing (the CHECK indicator is lit orange).
5. Stop overdubbing0start playback.
When in the overdubbing state, press the pedal switch to stop
overdubbing and transition to playback (the CHECK indicator
is lit green).
6. Adjust the volume.
Use the [E.LEVEL] knob to adjust the volume of the playback
sound.
7. Finish playback.
To stop playback, press the pedal switch twice. (If there is
recorded data, the CHECK indicator blinks green.)
* Press the pedal switch two times in succession, keeping the
interval between presses to one second or less.
Hold down the pedal switch for two seconds or longer
to delete the recorded content.
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