Dust Arp 32 (for 32 steps.. there is 64-bit version too, but Windows only) is a polyphonic pattern arpeggiator of sorts. It was original designed as a "MIDI level gate" but it quickly become obvious that it works as an arpeggiator too.
It doesn't do anything with audio: you feed it MIDI notes, and it'll send MIDI notes out (which you need to route to some sound generator).
Download here.
Since the original video was considered too confusing, here is a sort of tutorial. See the "youtube annotations" for descriptions of what is going on.
Basic description (explained in the video too) is that it takes the incoming MIDI notes, assigns them to the "rows" automatically, and then plays notes when the given step is set to have a note on that row.
Left-click will set short notes. Right-click will set ties. If there was already a dot of that type where you click, it'll draw in "erase" mode instead.
Gate sets the length of the "short" notes, while "ties" will end at the end of the step, unless there's a note at the next step (that is played, in case of jumps), at which point the two notes will merge into one.
Shift (with either button) will draw "monophonic" only.
Control (with either button) will affect "everything above" that row.
With both shift and control, everything above draws, everything below clears.
The horizontal slider below the dots will set the pattern length.
The vertical bars below that will set the velocities of the notes that start at that step.
It has some "intelligence" to try to do the "right thing" which can sometimes result in somewhat confusing behavior, but it tries really hard to avoid anything "bad" going on.. so you should always get something "sort of reasonable" even when you do random things on the fly.
There is full automation recording of everything (with a slightly confusing VST encoding), but be careful when automating both dots and pattern (preset) selection at the same time, as the automation playback will affect currently selected pattern, not the one that it was recorded for.
