Why wont soft synth changes appear in GB recordings?

Hi,

ive asked this before but I must be wording it badly.

Im trying to figure out why any soft synth can be recorded in GB and work fine to record the actual notes etc but when i try to alter say the resonation or filters fo rexample on specific notes or throughout a song none of these fine details come out in the recording. If I play a real synth and record that it works with all the konb alterations i make in realtime to a recording in GB , but all the soft synths dont seem to pick up the realtime changes i am making. Only the notes or chords. I can make the changes before i record apart but if I wanted to just add a bit of different resonation to an end note by hand as its recording it wont pick this up in playback. Can anyone help?