volume levelling

There is one problem I have. Sonce I get mp3’s from all over the Universe. it is often the case that they have different volumes. Now the version of WMP I have does not auto-level the tracks so that they have the same relative volume. 35 years ago some cassette decks had a feature called ALC. Automatic Level Control. This set things up so that the record level was the same for all tracks. Media Monkey seems to have something similar. Now, the problem is having something for the mp3 player

Right now, I use 

MP3Gain

However this is only an approximat ALC to +/- 1.5 db and I don’t know if it operates within a meddia player but it’s free and it’s OK

Are there ALC programs that do a better job and alter the file to keep the selected level no matter where they are moved or copied?