ok so in ableton u have midi effects for midi just the same way that u have vst effects for sound
that can be input into the 'signal path' at the bottom of the screen
naturally you would want to put this in to the left (before) the actual vst that is being sent the midi
data....
but here is an example of how this midi effect works in ableton live 4 on mac os 9
this dial + number + percentage..
the dial + number represent the same thing, which is based on note transpose from the root note.. so
to create a chord u are transposing operators (keys) however many dials u specify transposes for is how many keys the chord you hear willl be made from from pressing a single root key
here i have created a 5 key minor chord so u can see the 2nd key is transposed +3 , the 3rd +7, the 4th +10, and the 5th +14
if u press the down arrow in the top right hand corner of the chord midi effect u can also pick from some presets that they have included but i dont care for them much personally
for more info on the types of audio/midi effects in ableton
visit
https://www.ableton.com/en/live/?a=what_isif u scroll down a bit theres a horizontally scrolling section that visually shows different effects