hendrik on 05 Feb, 2019 08:17 AM
beaTunes can do loudness normalization by adding ReplayGain (and iTunNorm) tags to the file. It does not change the the file in any other way.
iTunes does not honor ReplayGain tags, but only iTunNorm tags and only when SoundCheck is on. So the first thing you need to do is turn SoundCheck on in iTunes (preferences -> playback). Then analyze your files using beaTunes for ReplayGain. To see the suggested gain, select a file in iTunes, open its Song Info dialog (⌘I), and go to the File tab. There you should see the gain adjustment in dB in the line volume.
hendrik on 08 Feb, 2019 09:45 AM
(Is there an actual manual somewhere?)
Yes. Once you've started the application it's under the Help menu. Admittedly, this is not 100 pages of prose, but all the basics are covered. Just to illustrate, I have attached a screenshot of the info about ReplayGain.