Mastering is the final step of an audio project before it's release. The purpose of mastering is to balance the audio content of the mix, eventually add some color and optimize the release on all related systems and media formats. 

Think of mastering as the glue, varnish and polish that optimizes playback quality on all devices—from tiny iPhone speakers to massive dance club sound systems. Mastering bridges the gap between artist and consumer. The term itself comes from the idea of a master copy. All copies or duplications of the audio come from the master. These copies can be distributed on multiple formats like vinyl, CD’s or Tape, and streaming services like Spotify, iTunes and SoundCloud. Additionally, mastering allows for the restoration of hisses, clicks or small mistakes missed in the final mix. Mastering also ensures uniformity and consistency of sound between multiple tracks on an album. Ultimately, what mastering does is create a clean and cohesive feeling across all your audio.

Why master?

The goal of mastering is to ensure that your audio will sound the best it can on all platforms. Music has never been consumed on more formats and devices than today.
One of the other main aspect of mastering is also to have your track reviewed by a fresh pair of ears, still objective on the project.  Who, if needed, will fix the issues or enhance it using high grade tools carefully selected.

A good mastering job also makes an EP/Album consistent and balanced across all tracks. 

So what does mastering do?

Mastering is a complex process. Here are some of the techniques involved:

Fixing any small clicks, clips or other similar issues .

Ensuring a proper Stereo Image

Ensuring a proper Tonal balance

Ensuring a perfectly volume optimized & dynamics respectfull master with enhanced perceived loudness, definition in the hits, punch & tightness.

Ensuring optimisation for digital release following the codecs specifications of each platforms.

Ensuring best Sample Rate/Bit depth for distribution using high quality Resampling & Dither if needed.

Ensuring Metadatas are properly inserted in the final files using appriopriate tools.

Ensuring good sequencing & spacing between multiple  tracks in a same project.