A neat thing about the ubiquity of cheap microcontrollers like the Arduino family is you can easily try this sort of stuff out at home. Given a MIDI interface

A neat thing about the ubiquity of cheap microcontrollers like the Arduino family is you can easily try this sort of stuff out at home. Given a MIDI interface and something to trigger, it's not hard to see how counting six MIDI clocks for every trigger will give you straight-ahead semiquavers (16ths) because MIDI clock runs at 24 pulses per crotchet note. With a bit of thought then you can see how pairs of semiquavers will be 12 pulses long, which you can split up any way you like. "50%" is obviously six and six, 58% shuffle would be seven then five, and so on. But you don't need to stop there. Imagine making a list with a velocity for each hit, and a "time to next hit" in clocks. As long as the total number of "time to next hit" added up to the right number of clocks per bar, the actual notes could be anywhere ahead of or behind the beat. If you deliberately used the wrong number of clocks, you'd end up with your pattern drifting out of step with the rest of the sequence, and if you do that right you've just (re-)invented polymetric rhythm.