Humanise will let you delay MIDI ‘note on’ and ‘note off’ events to make quantised music less perfect. You can set a minimum and random delay for both ‘note on’ and ‘note off’ separately.

To play e.g. a bass line slightly behind the beat, route it through Humanise and set the ‘MinOn’ value to 3 to delay all note ons by 3ms. If you also set the ‘RandOn’ value to e.g. 5ms, then each note on will be delayed by a random number between 3 and (3+5)ms

Each value (MinOn, RandOn, MinOff, RandOff) can be set to anywhere between 0 and 127, meaning your note ons and note offs can be delayed by up to (127+127=)254ms worst case. I don’t have a use for delays this high, but maybe you do.

All channel, note and velocity data will be preserved, and any CC or program change data will pass straight through unchanged.