Because BeOS 5 has an MP3 decoder built into the operating system, you can do cool things like dragging MP3s directly into CDBurner without decoding them to WAV or AIFF first (see screenshot). This makes it incredibly easy to make custom audio CDs from your existing MP3 collection.
But as you’ve probably discovered before, original CDs are recorded at varying levels. When you create a mixed CD, you find that the volume changes from one track to the next. Annoying. To fix this, select a track in CDBurner and adjust the Gain slider. You can use the Preview function to hear how the track’s volume now sounds relative to the previous or next track.
You can also adjust fade-in / fade-out lengths by using the red draggers in the lower part of the window, or enter them numerically into the right fields. Note, however, that some users have experienced static on the resulting CD when using the fade sliders in BeOS 5. Hopefully this bug will be fixed in a future release.

Joachim Seemer ( J.Seemer@gmx.de) adds:
Another great way to level the volume of a bunch of tracks is the commandline program BeNormal. This app, however, only works on WAV files.