If a recording artist has any hopes of their songs being played on the radio, it is vital that their rough mix is mastered well. Often the best way to do this is to hire a CD mastering engineer. Professional CD mastering engineers can make a decent mix sound good and a good mix sound amazing. There are several things that CD mastering engineers do. Engineers work with the artist to decide what order the songs will appear on the CD, and they equalize the volume of the different instruments in each song and across the whole CD. CD mastering engineers can also add more definition and clarity to the instruments on a song. They then adjust the intros and ends of songs, choosing length of time between songs and adding crossfades or other effects if need be.
The order in which songs appear on a CD can greatly affect the way the CD progresses when played. If similar sounding songs are placed consecutively on a CD it can suggest shortcomings in the songwriting or make listeners believe the artist has a limited range. Also, some CDs can tell a narrative if sequenced correctly. Ultimately, it is up to the CD mastering engineers to work with the recording artists and choose the song order on the CD.
It is important that the instruments within a song and the songs on the CD are at an appropriate volume level. Within a particular song, the different elements must be mixed appropriately in order for the song to sound good. The mastering engineer can give clarity and definition to the different instruments in a song. The engineer also has the task of assuring that volume levels across all of the songs are similar, to help the CD sound more cohesive while still leaving room for dynamics.
CD mastering engineers also determine how much time there should be between songs on the CD. They fade and crossfade the intros and endings of songs to make them flow better.
CD mastering engineers have the task of making a rough mix of a CD ready for public consumption by adjusting audio levels and pacing the tracks in a way that brings out the best in the material.