Yamaha Electone EL-900 Owner's Manual page 112

NOTE:
The parameter value can be changed
quickly when you press the Data Control
button with the COARSE button held.
8
112
2) To edit the FM Operators:
1
Adjust the Envelope Parameters of Operator 1 (after turning off the
other Operators).
The Envelope Parameters control the level of the sound and how
that level changes over time. See page 122 for more information.
For now, try making some of these changes in the envelope:
Adjust the OL (Output Level) parameter.
Changing the OL parameter affects the volume of the selected
Operator.
Raise the OL parameter from 0 to 110 by using the pair of Data Control
buttons just below the OL. (Pressing the A button raises the level,
and pressing the B button lowers the level.)
Adjust the AR (Attack Rate) parameter.
Play the voice and notice how the changes you make affect the initial
volume of the voice. By changing this parameter you can make the
sound gradually get louder (lower settings) or have it reach its full
volume all at once (higher settings).
Envelope
Parameters