[linux-audio-dev] Plugin APIs (again)

[Frank van de Pol]

On Sun, Dec 08, 2002 at 10:35:39AM +0000, Steve Harris wrote:
> On Sun, Dec 08, 2002 at 12:26:32 +0000, Nathaniel Virgo wrote:
> > I think velocity is special because it is often needed by the synthesis 
> > algorithm only at the beginning of the note.  For instance, if you have a 
> > physical model of a bell then the velocity will determine the shape and 
> > magnitude of the impulse function you use to represent the striker.  Changing 
> > it midway through the note, after the bell has been hit, is meaningless.
> 
> A Bell is a good example of something where you want multiple velocity
> events, you could call voice_on() or whatever to initialise the physical
> model instance, then you send simultaneous velocity and position events to
> indicate that the bell has been struck.
> 
> Its not true for a impulse derived bell but a weaveguide model of a bell
> struck twice has a different sound to a pair of identical ones each struck
> once at the respective times.
> 

Nice examlple. To me it clearly illustrates that velocity (ie. force of note
on/off) is indeed a property of the note event. The handling of velocity for
said bell depends on the implementation of the synth; a physical modelling
synth could when retriggering with the same pitch adjust the sound of the
bell. Simple sample playback synths would most likely not have this level op
sophistication.

The violin example using the bow speed property is something different. In
fact, the bow speed is indeed a sort of continious controller, while the
strings could be hit by the bow with different velocity. How could one
otherwise achive a pizzicato effect? (I might use the wrong phrasing, but I
mean hitting like slapping a bass guitar the violin's strings using the
bow.)

Though not in the scope for the instrument plugin discussion, I'd like to
see compatibility with MIDI or other real-life protocols be considered. In
the end our sequencer applications would need to transparently support both
flavours.


Frank.

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| Frank van de Pol                  -o)    A-L-S-A
| FvdPol at home.nl                    /\\  Sounds good!
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