The benefit is you can create sample-accurate arpeggios, amplitude-modulated timbres, and other extreme and unplayable effects famously (over)used in tracker music.
You don't seem to have experience of what trackers can do. Essentially Black MIDI is rendered tracker music with a nice animated piano roll background.
On a slow system a render will take longer than real time. On a fast system it won't.
> You don't seem to have experience of what trackers can do.
Well, I'm a trained musician and use sequencers since Atari times; a tracker seems to be just a sequencer more geared towards people who prefer to enter numbers instead of playing; if so I would prefer something like csound or chuck; but I was more interested in live music the last few years; here is what I currently do: http://rochus-keller.ch/?p=1153
