I think midi implementation is by far the trickiest part of max. So far I’m feeling really discouraged at transforming my stand-alone monosynth into a polyphonic midi device. It’s almost like I need a class on Max/MSP midi connectivity
A common solution is to [pack] control data and use the [target $1, $2 $3..] message(s) to the [poly~] inlet; you can of course add as many poly-inlets as you need. Peter Elsea (as well as Chris above) have provided some excellent ‘realworld’ examples of polyphonic midi-synths, using the [poly~] object.