This is a list of the envelope inserts. There are 4 types of these, some only having
a few of the controls. They are shown below with their controls. 'Par' is the
parameter number that must be sent and 'Con' is the control number.

Par     Con
0   Amplitude
        1   Attack time
        3   Decay Time
        4   Sustain Value
        5   Release Time
        7   Stretch
        16  Forced Release
        17  Linear
        32  Enable Freemode

1   Frequency
        0   Attack Value
        1   Attack Time
        5   Release Time
        6   Release Value
        7   Stretch
        16  Forced Release
        32  Enable Freemode


2   Filter
        0   Attack Value
        1   Attack Time
        2   Decay Value
        3   Decay Time
        5   Release Time
        6   Release Value
        7   Stretch
        16  Forced Release
        32  Enable Freemode


3   Bandwidth (only apples to SubSynth)
        0   Attack Value
        1   Attack Time
        5   Release Time
        6   Release Value
        7   Stretch
        16  Forced Release
        32  Enable Freemode

For all of these the insert value is 2.

Refer to "Yoshimi Control Numbers.ods" for more detailed control layout.

Freemode behaves quite differently and when enabled, the following controls are used
instead, and are the same for all envelopes (although 'Stretch', 'Forced Release'
and 'Linear Envelope' are as before).

There is additional control number 34 that returns the number of defined graph
points in 'offset', and control number 35 that detirmines which point on the graph
is the release point (and can only be in the currently defined range).

The axis graph controls are 'Add point' and 'Delete Point' Both of which have Insert
value 3. Also, 'Change Point' has Insert value 4.

All of these use 'Control' to define the graph point being accessed. For 'Add' and
'Change' 'offset' is the X axis increment and 'Value' is the Y axis value. When
deleting a point 'offset' is 255.

Out of range or errors usually return X and/or Y as 0xff.
