For live performance, I'm trying to create a setup whereby I use a mono melody track to run thru the scale and chord midi effects into an arp (either the midi effect or an arp preset in a vst). Is there any way, within Live or using a Max plugin, to isolate, e.g. the first note of a bar to generate the chord and hold it throughout the bar, ignoring the subsequent notes, which otherwise keep re-triggering the arp? This way I only have to make sure that the first note of the bar is the root note of the chord I want held for the remainder of the bar, Any ideas, or a way to do something similar?
Isolate it by velocity perhaps. Make sure the sustained note is at a fixed velocity and that the other notes can't hit that velocity. All doable with Rack Layers, Chord and Velocity plugins. Then filter the velocities with a MIDI Rack. Probably easiest to set the first note at Velocity 1 and crank it up after its filtered.
If you actually require velocity expression on that first note, maybe MFL might be better suited.
Though I'm not excluding that a more elaborate MIDI Effect Rack might do the trick.