During mastering, the audio engineer, sometimes known as the mastering engineer, will work on the combined version of the track and treat is as a whole to create a more professional sound. The three main focuses of the mastering engineer are the overall sound of a track or album, consistency across all tracks on an album, and preparing for distribution.

With regards to sound, the mastering phase uses several tools to produce a more complex track with increased depth: Equalizers, reverberation (“reverb”), compressors, and expanders.

Each of these tools affects the tone and frequency of the track in its entirety. The audio engineer will also correct any issues with song’s balance to create a polished end product.

The audio engineer will also take into consideration how each song sounds in its particular position on an album and make any adjustments to allow for smooth transitions. To keep listeners from constantly needing to adjust the volume, levels across all tracks are checked for consistency.

In the last phase of post-production, an audio engineer prepares the song or album for download by converting it to the delivery format that the listener will purchase. Different formatting options require different tweaks to maintain quality sound.