Boss RC-20 Owner's Manual page 14

Recording a phrase from CD/MD to create a phrase loop
6. Press the left pedal to begin recording.
If the AUTO START button is on, recording will begin the moment the CD/MD
begins to play.
If the AUTO START button is off, recording will begin the moment you press the
left pedal. Listen to the sound of the CD/MD, and press the left pedal at the
appropriate time.
* If the internal memory is used up, recording or overdubbing may stop before you are
finished. If this occurs, erase unnecessary phrases (p. 23), and try the operation again.
7. Press the left pedal to stop recording.
Simultaneously, the recorded phrase will begin playing. The tempo of the phrase
will also be set automatically.
* The automatic tempo setting is calculated with a time signature of 4/4. If you are
recording a phrase whose time signature is different, you must re-specify the correct
tempo after recording (p. 24).
* If you recorded an extremely short phrase, the length of the phrase will be adjusted
automatically, and then recording will stop (p. 27).
8. Press the WRITE button, getting the indicator to start blinking. When you do
so, playback will stop automatically. To save the data in the same phrase
track, press the WRITE button once again.
If you wish to save the data in a different phrase track, press the WRITE button (so
its indicator is blinking), use the PHRASE SELECT knob to select the desired save
destination, and then press the WRITE button once again.
* For details on saving, refer to "Saving a phrase" (p. 23).
9. Press the MODE button to select how overdubbing will occur.
As you did in step 2, select the overdubbing method. If you wish to overdub a
performance from guitar or mic, select INST & MIC.
10.Press the left pedal to begin playback.
11.When you wish to overdub (p. 10) along with the phrase, press the left pedal.
Each time you press the left pedal, you will switch between playback and
overdubbing modes.
12.To stop playback and overdubbing, press the right pedal.
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We recommend that you save the phrase at this point. If you are not
content with the results of subsequent overdubbing, you can then
cancel only the overdubbing.