It sounds like you are attempting to have all the music play at the same volume, but this would not be right. I don't expect a Haydn string quartet to make as much noise in my car as, say, Metallica. Some music is supposed to sound louder than other music.

You are right. That's why I like the idea of having some sort of "global gain" attribute stored with each song in the empeg's database, with no changes to the actual music data. There could be a function in Emplode to analyze the average volume of a song and then make a proposal for that attribute, but the user would be able to manually change it, or not have it set at all.

In my eyes this combines the advantages of many of the proposals here: rather easy to implement on the empeg side, no distortion due to re-evaluating the music data, total user control over the result.
As an extra bonus, this attribute could be taken from the corresponding ID3v2 Tag value if it exists...

Regards
Daniel