A couple of days ago I grabbed the microKorg owner's manual to read on the throne. I happened to open to  Page 61 - Assigning control changes(CC).  It says you can assign numbers to the principal parameters. The edit menu section on the microKorg is shown with the principal parameters highlighted.

You can assign the CC# or just use the defaults that are assigned to those parameters.  These are listed in the Table on page 56.  The Control 2 values when OSC1-WAVE = DWGS are within the table on page 57 and the names for the DWGSs are listed on page 20.   (Digital Waveform Generator System(DWGS))

I thought it would be handy to have a table of the default CC# that would match up the layout on the Korg.  This PDF contains a table for the SYNTH commands and parameter changes.  I hope it can be of use as a scratch pad when programming control changes from the Atari.

MicroKorg - CC defaults.pdf

The sheet wasn't of much use for this small example Atari BASIC program.  It uses CC#77 to change the OSC1-WAVE synth parameter.  It will change the wave to Saw, Square, Triangle, Sine, DWGS, or Noise, after the computer menu number is entered.

A CC command requires three bytes of data to be sent to the synth.  The first is the command type(176) + channel-1. The second is the controller number. The last being the setpoint;  0-127 but data can be used however the synth is programmed.

In this example Atari BASIC program an array is filled with the CC setpoints that will change the wave form on the microKorg(30020) and then the I/O channel 1 is opened for the M: device(32010-32030).  A menu is displayed on screen.  Input the number of the desired wave and the command will be sent(260).  Play the microKorg keyboard and you should notice some change in the patch. (Do I have to make mention that the microKorg has to be connected to the Atari through a MidiMax compatible interface?)

Changing the wave on patches does make some surprising changes to the sound.  Any changes that are made will not be permanent unless you save the patch.  Keep the write protect on while experimenting and you shouldn't have a problem.

CC77.BAS

1 REM microKorg OSC1-Wave CC Code 77

2 REM by Kevin Packard 4/22/2020

3 REM

4 REM Some panel knob/keys can have

5 REM a CC# assigned to them. This

6 REM program can change OSC1/Wave,

7 REM which effects the patch.

8 REM

9 REM Requires MIDIMAX type interface

10 REM MicroKorg and M: device.

12 REM

100 GOSUB 30000

200 GRAPHICS 0:?

205 ? "WAVE TYPE:"

210 ? " 1. SAW":? " 2. SQUARE":? " 3. TRIANGLE":? " 4. SINE":? " 5. DWGS":? " 6. NOISE":?

215 TRAP 220

220 ? "INPUT WAVE TYPE >";:INPUT X

230 IF X<1 OR X>6 THEN 220

260 PUT #1,CMD:PUT #1,77:PUT #1,WAVE(X)

270 GOTO 200

29999 REM set up parameters

30000 GRAPHICS 0

30010 CMD=176+0:REM CC+channel-1

30020 DIM WAVE(6):WAVE(1)=0

30030 WAVE(2)=18

30040 WAVE(3)=36

30050 WAVE(4)=54

30060 WAVE(5)=90

30070 WAVE(6)=108

32010 CLOSE #1

32020 OPEN #1,13,0,"M:"

32030 XIO 40,#1,0,0,"M:"

32040 RETURN

ATR contains DOS 2.5, the Autorun.sys sets up the M: device, and CC77.bas

KORGCC.atr

When you BREAK from the program be sure to "CLOSE #1" before trying to access the disk drive.