[iiwusynth-devel] SF2.01 technical specification: GM default modulator vel => filter

[M. Nentwig]

Hello,

I'm currently working on a SF2 compatible software synthesizer. I have a
problem in understanding section 8.4.2 of the specs (version 2.01).
There, a modulator is described, which lowers the filter frequency by 12
semitones between MIDI velocity 127 and 64. But what then? The secondary
modulator is a switch, which turns '0' at velocities below 64. So the
filter jumps back to its nominal center frequency.

My two questions are:
- How is this modulator to be implemented (what is the reduction in
filter frequency at vel=127 - probably 0, vel=64, 63 and 0?
- What is the correct definition for this modulator (in terms of primary
/ secondary type, polarity, direction)? The point is, that a sound font
has the option to overwrite the default modulator. I could easily get a
working implementation, for example by using two modulators, one of them
switched. But if I change the controller definition 'to what sounds good
to me', this will not work anymore.

I'd appreciate any help here.

Best regards

Markus Nentwig




PS: The web page mentions a version 2.1 for the specifications, but all
I can download is 2.01. Is there maybe a later version, which answers my
question?