AW: crap Synth idea-DIY

Haible_Juergen#Tel2743 HJ2743 at denbgm3xm.scnn1.msmgate.m30x.nbg.scn.de
Fri Mar 1 01:00:00 CET 1996


>- just because I have spent
> approximately 800 hours in the past year dealing with keyboard > scanning 
and
> the programming of mono and polyphonic voice assignment > algorithms, and 
chose
> to voice my opinion on the usefulness of building your own keyboard 
>decoding
>circuitry, doesn't mean that *you* can't go ahead and build one if you

I'd love to hear more about these things - the logic behind different
key scanning algorithms !

>BTW, the only poly (more than 2 notes of polyphony, that is) keyboard I >am 

>aware of that doesn't use a CPU is in the CS-50/60/80, and that uses a
>custom Yamaha LSI chip to do the trick.

Let me say Oberheim 8-voice, Emu polyphonic keyboard (ok, the same
one, almost, I admit!)

>Detecting which keys are depressed are the easiest part of the >problem.
>Then you have to decide how to assign notes to a (presumably) limited
>number of voices.  Unison, rotating, nonrotating assignments - how are
>you going to do this in hardware?  These are difficult enough to
>implement in software.

Unfortunately, my schematics of the n-voice scanning logic are barely 
readable, so I haven't figured everything out. So once again, every
information about the logic behind different assign modes (regardless
of a CPU/non-CPU implementation!) is highly welcome! I encourage
you to share all you know about this topic!

(And yes, I have considered building a discrete (i.e. MSI CMOS)
polyphonic keyboard scanner myself, now and then. But I still
lack the information I need for this!)

JH.



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