Mastering is as important as any other step in the recording process-and by all means-BE THERE WHEN YOU MASTER IT-if you can...or send it to someone who understands the music you're playing and won't fuck with the vibe...mastering just takes whatever you did-that you like-makes it EVEN-each song-as every song-even though you recorded for instance 12 songs the same way-same sessions-each song is at a slightly different level, because when you mix each song, you may get a great vibe, but then notice that some songs aren't as loud -which is normal-then mastering just levels it all out-brings out the best tonal quality. I remember when a friend didn't master his album-and you had to turn up certain songs-this way you don't have to do that-