Polyphonic Aftertouch is the only MIDI parameter that allowed for independent control over the timbre of a single note over its whole duration already since the establishment of the MIDI standard in the 1980ies.

It is however only implemented into a handful of synths. If you are lucky and a synth that you own supports it, then you can map one of the expression zones of Osmose’s Augmented Keyboard Action to it.

Notable examples for synths reacting to Polyphonic Aftertouch are recreations of iconic synths like the Yamaha CS-80, no matter if software or hardware. But there are also more current synths like the Dave Smith Instruments Prophet REV2 or Novation PEAK that will react to Polyphonic Aftertouch.

Attention: The term “Aftertouch” is also used mistakenly, but very commonly, for the parameter “Channel Pressure”. This parameter however only allows control a global basis for all notes being played (hence the name, it is affecting the whole MIDI channel).