First off: This may not be a MusicBee problem...
My MP3s have all been tagged with volume leveling information using the MP3Gain utility. Recently, while still using the "MediaMonkey" player, I began having volume level problems. So, I re-ran MP3Gain on my entire collection with no change to the symptoms. Figuring it might be a new bug in Media Monkey, I switched to MusicBee, but still heard the inconsistent volume. Finally, I ran MusicBee's volume analysis utility on the entire library, but it seemed to make no difference.
I could have some kind of hardware problem - but the volume change ONLY happens between MP3s - which makes me think it's software.
Can someone suggest some steps I might take to see where the problem lies?