Mastering is the optimising of tracks for final processing/playout.

With only one track, the only consideration is how loud that track is when you put it in the machine and play it. You may notice that CDs vary in volume from one disc to another. The quieter ones are not using the full range of digits available to store the sound. Sometimes this caused by the track(s) having high but transient sounds which DO use the range briefly and cause the overall and average volume to be lower.

In this case, mastering might consist of compressing or limiting the one track so that the general volume can be higher. I think that most people on this list would advise that compression and limiting be approached with great care as it does affect the sound - sometimes adversely and sometimes to advantage. Your ears will be the judge.

There is also a process called 'normalising' where the computer recalculates the waveform so that the loudest sounds use 100% of the available volume range, making the track as loud as it can be without digital distortion.

Your engineer will advise you on all these things but it's mostly down to common sense - when you play the CD does it sound as loud as the last one you played? If you play it and it sounds ok, it IS ok.

Hope this helps.

J