In the vast majority of cases when you change key or tempo in Song Surgeon you hear no distortion
of any kind.  However, in a few cases clipping may occur.

When you open the file in Song Surgeon if the data in the center of the Song Surgeon windows
pushes the boundaries of the graphic window, it is possible such a file may clip.

When you change key or tempo, SS must by definition modify this wav form data to accomplish the
task. Thought the changes are very minute, in some cases it is sufficient to cause a track to compress.
The solution for this is before exporting to move the volume slider downward to about 90%. The volume
slider controls the volume on export.

By reducing it you will reduce the volume and that should reduce thee amplitude of the wav form data
and stop the clipping.