Making volume conIsistent

Question from a newbie: I am recording organ music (small home electric organ). The volume from the organ is consistent throughout the piece of music. However, when I record the piece, on playback the volume starts out relatively loud, then seems to adjust itself downward as the piece progresses. If there is a rest (brief moment of silence in the music), the volume pattern repeats itself. When I use Normalize or Loudness Normalization, it adjusts the volume proportionally over the whole piece. Is it possible to make the recorded volume more or less even? Thanks.

That can be caused by Windows Sound “Enhancements”. See here for how to turn off all of the “enhancements”:

Excellent. This simple solution did the trick.