Ah, I think I remember now. The SET is used to specify the keyboard range that you can play that sample on.
In the screenshot in the post above, I mapped a collection of Mellotron choir samples across a 4 octave range. The samples were split into every A, C, D# and F#. So I made each one the centre of a 3 semitone range (except for the top and bottom), as follows:
F#2 from C2 to G2
A2 from Ab2 to A#2
C3 from B2 to C#3
D#3 from D3 to E3
F#3 from F3 to G3
A3 from Ab3 to A#3
C4 from B3 to C#4
D#4 from D4 to E4
F#4 from F4 to G4
A4 from Ab4 to A#4
C5 from B4 to C#5
D#5 from D5 to C6
Having gone through the ball ache of configuring that, I saved it off and now recall is just an ASL requester away
Regarding capture, MIDI In is not a sequencer, it's just a software sampler. If you want to use it to create any tunes, you need to use it as a slave to another machine running say OctaMED.
If you recall this:
Basically, the towered A1200 is running MidiIn and the desktop one is running OctaMED and controlling it over MIDI.
The MIDI tracking feature in midiIn is, as I recall, just to make the UI sliders (Pitchbend etc) and stuff update with the incoming MIDI data.