[sdiy] Continuous controllers

[George Hearn]

In all my experience with commercial equipment, when multiple continuous
controllers are received (say from external midi AND local keyboard)
together the system usually responds to the 'newest' value received.
Consequently controller data can become garbled.  I think a better scheme is
to select the 'greater of the two' where appropriate.  For example if the
user on a local keyboard applies a pitch-bend of less than the recorded midi
playing back, then it is ignored.  If however the user opens the cutoff knob
wider than the recorded controller then this is taken as the value and the
recorded data ignored.  
	As far as MIDI data rates for continuous controllers I'm not sure..
I know that I have experimented with scanning knobs and that the data rate
required for smooth sound on fast movements is much less than I expected.
MIDI wasn't really designed to produce real-time signals (like applying LFO
to the brightness controller for example), and so I should be surprised if
you see any data rates for continuous controllers going much above 100Hz..
but again I wouldn't be able to say for sure.

-----Original Message-----
From: synth-diy-bounces at dropmix.xs4all.nl
[mailto:synth-diy-bounces at dropmix.xs4all.nl] On Behalf Of Tom Wiltshire
Sent: 22 October 2008 22:21
To: synth DIY List
Subject: [sdiy] Continuous controllers

Hi All,

A couple of questions about MIDI continuous controllers;

MIDI continuous controllers like pitch bend and aftertouch aren't  
really continuous, since MIDI is a digital serial protocol.
Does anyone know how often these messages are sent typically?

Presumably the answer to this question is variable over time (1980's,  
1990's, 2000's) and between manufacturers. I remember hearing some  
digital synth years ago that had audible stepping on the pitch bender  
if you whacked it about a bit. Presumably modern ones are better in  
this respect. But sending information too often (or at too high a  
resolution, say with multi-byte NRPN messages) is just going to clog  
up your MIDI stream. For example, a later Moog Voyager OS update  
included a feature to reduce the amount of data sent by the touch pad.

The second question is related;

What happens if a piece of equipment receives two different sets of  
continuous controller data?
For example, playing back a piece of music with pitch bends and  
aftertouch, whilst also having active pitchbend and aftertouch coming  
from the local keyboard.
How do you decide which to use?

If anyone has any experience or thoughts to offer in this area, I'd  
love to hear.

Thanks,
Tom


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