Currently only one instrument on the Tracker can be played via MIDI with 8 voice polyphony (using all 8 tracks of the tracker) in MIDI Synth Mode.
And you should be able to changes parameters for it via MIDI CC, including the Filter Cutoff (see: Tracker Manual - Polyend for supported CC messages in MIDI Synth Mode).
There is an open wish to be able to change the instrument via MIDI:
Multi-timbrality however, will not be something that we will see: