The Channel Midi designations are not changed between songs unless some action is taken to reset the Synth. Settings such as Pitchbend, Modulation and Expression are carried forward and can cause distortions in the following song(s). When working with Midi files which contain the above Midi controllers, it is useful to start each track with CC 121 Value Zero which will reset all controllers. When auditioning Midi files and I have this problem, I can reset my Ketron SD2 by turning it off an on.