Yamaha Electone EL-87 Owner's Manual page 119

CLEAR
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The Clear function is used to erase an instrument from the
rhythm. All instances of the selected instrument, irrespective
of which tracks they occupy, will be erased from the pattern.
There are two ways to use Clear:
[1] While holding down the Data Control button
corresponding to CLEAR, press the key on the keyboard
corresponding to the instrument you wish to erase. (A short
"beep" sound indicates that the instrument has been erased.)
You can erase all of the sounds on all recorded tracks of the
pattern by holding down the Data Control button
corresponding to CLEAR and simultaneously pressing the
lowest key (C1) on the Lower keyboard. Be careful not to
do this inadvertently since all sounds will be instantly and
permanently erased.
[2] Press, then release the Data Control button corresponding
to CLEAR. The following display appears, prompting
confirmation of the operation:
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Then, use the step forward and step reverse controls to advance
or reverse the rhythm clock to the point at which you wish to
enter the percussion sound.
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