I really need to freshen up on my musick vocabulary. You just lost me with part of that, but I think I get your meaning.
For the sake of clarity, I'll try and explain a bit better. As you already know, OMSS uses "Instruments" rather than samples as used by many contemporary trackers. In OMSS, An instrument can be a sample, synthsound or a MIDI output channel.
In your example video you showed how to use an external MIDI device from OMSS by defining successive Instrument slots in OMSS as output channels.
All GM compatible MIDI instruments will, by default, play normal instrument sounds on channels 1 to 9 and 11 to 16, with channel 10 playing different percussion instrument sounds for different notes.
MidiIn is a MIDI controlled software sample player. How it responds to MIDI input is pretty much up to you. The key points are that it is multitimbral (can play multiple different samples at the same time) and that it supports a variety of keyboard splits. Suppose you have couple of nice bass sounds, but they only sound decent in the low octave ranges. You may feel it's a bit of a waste to reserve a whole MIDI channel (as you only have 16) for each one. Instead, you'd like to play them all on channel 1. You could have them assigned to different MIDI preset numbers, but on OMSS, you'd either have to remember to send the MIDI preset change messages when switching them, or assign them to different OMSS instrument slots bound to the same channel. Both work, but can be a bit wasteful.
However, MidiIn will allow you create "keyboard splits", where you map different note ranges to different samples on the same input channel. For the scenario above, this is rather more convenient. You can play your first bass sound using octaves 1-3 and your second bass sound in octaves 3-5 and your third bass sound in octaves 5-7, all on the same MIDI channel and only using one Instrument slot in OMSS.
You can take the idea to it's logical conclusion and create keyboard splits where each note plays a different sample. That's great for creating custom drum kits.
Or you might have some sound libraries of real instruments that have been sampled at several different notes. The Amiga's traditional IFF instrument format supported a simple version in which you could have a discrete sample for each octave. Modern sample libraries tend to use a sample every few semitones. It was this that I had configured MidiIn for in the screenshot I linked. I had 12 samples taken over a 3 octave range from a real Mellotron, giving a sample every 4 semitones.
Consider just octave 3 for a moment. I had samples for C-3, D#3, F#3, A-3 and C-4. I split the keyboard around these notes as follows
B-2, C-3, C#3 -> use the C-3 sample
D-3, D#3, E-3 -> use the D#3 sample
F-3, F#3, G-3 -> use the F#3 sample
F#3, A-3, A#3 -> use the A-3 sample
B-3, C-4, C#4 -> use the C-4 sample
repeating this same pattern across several octaves, using a total of 12 such samples. All of which, were a single Instrument as far as OMSS was concerned.
BTW Muffles = Miggies. Damn iPod spell correction! :/
And yet, somehow I understood it to mean that all along
