[LAU] Yoshimi, SubSynth, PadSynth, MIDI Learn

Hello, Listers-- I've successfully mapped two of my MIDI knobs to the filter's cutoff frequency controllers in both SubSynth and PadSynth. The problem is that in neither of these engines does the sound change continuously. The controller on the GUI moves when I twist the mapped MIDI knob, but I need to strike the key, again, to hear how the sound has changed. Apparently, filter sweeps are not allowed in either of these engines? This is not a problem in AddSynth. Some further details: OS: Ubuntu Studio 18.04, LTS Yoshimi: 1.7.4 Controller: Akai MPK88 Have I missed something? I will continue to search the manuals, lists, and other docs. Thank you! Tom