Yamaha Electone EL-87 Owner's Manual page 86

(4) Changing the Tempo
You can change the tempo of the song as the song is playing
on the M.D.R. by holding down the SHIFT button and
pressing the TEMPO + or TEMPO - button. (The Tempo
dial on the Electone panel cannot be used to change the tempo
on the Music Disk Recorder.)
Each press of the button slows down or speeds up the tempo
by a small amount. Changing the tempo does not change
the pitch of the music.
To restore the original recording tempo of a song, hold down
the SHIFT button and simultaneously press both TEMPO
buttons.
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N O T E :
When tempo is changed, the LED display indicates the
change as a percentage of the original recording tempo
(100). Values less than 100 indicate a slower tempo;
values greater than 100 indicate a faster tempo.
N O T E :
Tempo changes remain in effect even through changes
in song number. If you have changed the tempo in one
song, you should perform the above step to restore the
original tempo before playing another song. Turning
the power switch off and on again also restores the
original tempo.