After you’ve installed MP3Gain, open it. Click the Add Folder button and point it to the folder which contains all your music. MP3Gain will then proceed to scan for all your music.

Once it’s finished scanning all your music, press the Track Analysis button. MP3Gain will now analyze the volume levels of each track. Any tracks that are highlighted in red have a volume level that is too high and may cause distortion when you try to use the equalizer on your MP3 player.

After that’s done, click on Track Gain. The DB of all your songs will be altered to the value in the “Normal Volume” field. Any changes made in MP3Gain can be reversed. To do this, select Undo Gain changes from the “Modify Gain” menu.

That’s all there is to it! Now all your tracks will have a consistent volume level.