Because E-MU has such complex filters (the Morphing ones) they take a high amount of CPU cycles to calculate, all of which must happen at the same time your music is playing back. To help keep the strain of calculating those filters from affecting the timing critical playback of your Songs or Patterns, some compromises had to be made. In the case of the Command Stations, Resonance is fixed at note on, and cannot be changed while a note is held.