In a nutshell, mastering incorporates all of the audio work done on the master output from a mixed song or album. While originally intended as the mechanical preparation step for putting music into its final media format for playback, mastering later began to include additional post-mixing audio enhancement work in order to optimize the sound specifically for the various intended playback formats (ex: vinyl, CD, digital, etc.).
As we can see, we can divide modes in Major and Minor modes and this will affect the comparison we must make with their parallel scale. For example: E Phrygian is a minor mode, therefore it should be compared to E Natural Minor and not E Major. By doing so, we would find out that the two scales differ from each other by one note: F in the Phrygian mode instead of F# which appears on the E Natural Minor scale.