With an IDF (Instrument definition file), I can have the sequencer change things for me automatically like distortion on/off, or even change the tone I'm using (i.e. from 12A to 10B). An IDF is just a text file telling the sequencer what the specific commands are, and how to send them. So in essence, I can have one set up for rhythm, and when it comes time, change to a lead without having to stomp a button.
It is used for the sequencer, not to edit tones, and by change settings, I meant to switch from one to another. Just like having the sequencer play a midi note, it can also turn flanger - distortion - etc..on/off.
