[comp.sys.mac.programmer] MIDI Management Tools...errata

viking@silver.bacs.indiana.edu (Jon W. Backstrom) (08/29/89)

Rethinking Visualization
------------------------

In article 25132, viking@silver.bacs.indiana.edu (Jon W. Backstrom) writes:
>
>One complaint I have about Patchbay is that when two modules are
>connected straight across the bay, but at an angle, the connections
>are visually crossed.  For example:   
>
>Angled across...visual crossing of 'patchcords'...
>
> MIDI   > ------------------+                   +-- < SimpleKey
>Driver  < ------------------|-+      (Merged   /
>                            | |       Input)  |
>                            | |                \
>                            +-|-----------------+-- > MIDIArp
>                              +-------------------- <
>
>When you get a lot of merged inputs and cross-connections, it gets
>harder to figure out what's going on.  I would suggest that Apple
>should use a non-crossing visualization scheme for showing patchcord
>connections across the patchbay.
>
>Angled across...*no* visual crossing of 'patchcords'...why not?
>
> MIDI   > --------------------+                 +-- < SimpleKey
>Driver  < ------------------+ |      (Merged   /
>                            | |       Input)  |
>                            | |                \
>                            | +-----------------+-- > MIDIArp
>                            +---------------------- <


By exploring further, I find that I may have embarrassed myself in
that I can unscramble the mess simply by rearranging the modules
within the patchbay:

SimpleKey > ----------------   (Merged Input)
                            \
                             +---------------------- > MIDIArp
                             | +-------------------- <
                             | |
                             | |
  MIDI    > -----------------+ |
 Driver   < -------------------+          

I can grant that it's probably too much of a programming hassle to
implement a visual unscrambling scheme, covering all cases where
patchcord connections might cross, but the ideal would be to minimize
crossing *wherever* the modules happened to be placed in the Patchbay.


All Notes Off - possible bug?
-----------------------------

>Finally, the "All Notes Off" button, from the MIDI Driver Settings
>dialog (you get there by double-clicking the Driver icon in Patchbay),
>seems to send an all notes off message (B0 7B 00), followed by 128
>individual note off messages (80 nn 40 ... nn being 0-127), for *every
>MIDI channel*!  (1-16)  

As mentioned, a large stream of data seems to be produced...an "All
Notes Off" channel mode message (Bn 7B 00) followed by 128 individual
"Note Off" messages...for each MIDI channel.  (6192 bytes, in theory)

I assume that individual "Note Off" messages are used for those synths
that might not respond to the Channel Mode "All Notes Off" message.
Is this true, Apple?  (Is all this data *really* necessary and would
you consider toggling this behavior in the next implementation of the
MIDI Driver?)

I tried to describe how I physically looped the MIDI OUT to the MIDI
IN (using an external MIDI cable) and then used SquidCakes (the simple
MIDI event recorder) to look at the output after the "All Notes Off"
button from the MIDI Driver Settings dialog was pressed.

My results were inconclusive, however, due to the inherent slowness of
the MIDI recorder.  SquidCakes records data for channel 1, 2, and the
first part of 3...sometimes missing the initial channel mode "All
Notes Off" message (B0 7B 00).  Spurious data appears in the recorder
at the end of each burst and the "MIDI Communication Error", produced
on my Roland D-50 when 'listening' to this "All Notes Off" message in
OMNI mode, makes be suspicious.

Has anyone looked carefully at the output of the Apple MIDI Driver's
"All Notes Off" command?  Does it actually send 6192 bytes of data?
Are all the MIDI messages legal, or does the data stream contain bogus
packets?

-------------------------------------------------------------------------------
 Jon W. Backstrom                 "Yah sure...we gonna have fun, you bet!"
 Institute for Digital Arts
 P.O. Box 176                     Internet: viking@silver.bacs.indiana.edu
 Bloomington, IN  47402-0176      UUCP: {ames,rutgers,att}!iuvax!silver!viking
-------------------------------------------------------------------------------