Album Mastering
When it comes to mastering big projects of multi songs, a lot of care must be abided by. Sometimes you can get a bunch of songs that have been recorded at different locations, studios, live outdoors or indoors. The impact these things have on the mix means the mastering engineer must be aware of the differences if any, so adjustments can be made for every song.
Another aspect of an album to be mastered is that it could have been recorded entirely acoustic with just microphones. Since there is no way to adjust levels or stereo pan individually, the mastering engineer would use EQ to bring out all the sounds the best way possible.
It is also important that the engineer takes care to pace him/herself between songs an not try to master more than one song at a time. Every song requires it's own unique special attention. Plus you have to take in to account the requests of the artist an their expectations of what they want the final sound to be like.
Great care must be taken to make sure there is a cohesiveness for the entire project so that it sounds like it was all done in one place. This will be perceived in the loudness levels, EQ, processing & effects that were used. The options take many paths since mastering is an art where creativity can play a part in producing a great final product in the end.