What Is Mastering?

In audio production, mastering is the final stage after mixing. There are usually two stages in the mastering process:

  1. Polishing the sound.
  2. Preparing for distribution.

Polishing The Sound

Polishing the sound is achieved by correcting any mix balance issues and enhancing particular sonic characteristics. This can involve:

  1. Adjusting levels.
  2. Adding compression to manage overall dynamics and increase the overall level (loudness).
  3. Stereo enhancement for a more impressive sonic sound.
  4. Equalization to bring the song (or songs) together.
  5. Removal of pops, clicks and other sonic mistakes missed during the mixing process.

The mastered track should always sound better than a finished mix.  The end goal is to ensure the sound is at its absolute best. 

When creating an album, it's essential to master all the tracks together to achieve a cohesive feel.

Distribution

The second step in the mastering process usually involves preparing the song or album for manufacturing and or download.  The finished product should be optimized for playback across all systems and media formats.

In the case of a CD, it can mean converting to 16 bit/44.1 kHz audio through resampling and/or dithering, setting track indexes, track gaps, PQ codes, and other CD-specific markings. For online distribution, you might need to adjust the levels to prepare for conversion to MP3 and include the required metadata.