It all depends on what you're trying to do:
- Use the iPad to record your audio while playing the MicroKorg and have the SR18 play to the same clock rate as the LFO on the keyboard.
- Using a Sequencer / DAW on your iPad to sequence the sounds in the MicroKorg and SR18 as sound modules, whilst using they Keyboard on the Micro Korg as your controller.
- Or something else....
Being a synth nerd myself long before plug-ins were a thing, connecting this for situation number 2 would be as follows:
- Alesis SR18 Audio Out to Input 1 on iTwo
- Micro Korg to Audio Input 2 on iTwo
If you want the MicroKorg to be your MIDI Controller
MIDI Setup would be:
- MicroKorg MIDI Out to iTwo MIDI IN
- iTwo MIDI Out to MicroKorg MIDI In
- MicroKorg MIDI Thru to SR18 MIDI IN
Your MicroKorg is Multi-Timbral (Channel 1 for all keys) or 2 Channels when using the Split Mode Channel 1 for lower half, Channel 2 for upper Half.
From your sequencer you'll need to choose your patches for the Korg to trigger on MIDI Channel 1 and your Drums can be programmed by using MIDI Channel 10. Note to prevent doubling of sounds (playing sound locally on keyboard and triggering from the sequencer) You'll need to turn off Local MIDI control on the Micro Korg (see owner's manual on how to do this), then your Micro Korg doesn't produce any sounds when you press a key, you'll need to select the patch from your sequencer to tell the incoming MIDI data which sound to trigger on the Micro Korg synth engine.
If this is all new to you, you'll need to take some time to learn more about how MIDI works.
- Read your MicroKorg manual
- Read your SR18 manual.
- Watch some YouTube videos - Learn Basics of MIDI and differences between Audio and MIDI
- Learn about MIDI Thru / MIDI Merge boxes
- Once you know the basics of MIDI, then it's a matter of Trial and Error, plug it in and figure it out and have fun while doing it.