Updated: Mar 24, 2022
I am not here to claim that mixing or mastering is easy, or that everyone should be doing it for himself or herself. I make my living primarily mixing and mastering for others, so I certainly believe that hiring an experienced mixing and/ or mastering engineer might be the best production decision you can make. Nonetheless, I believe that effective mixing and mastering are not beyond the capabilities of anyone seriously interested in doing these things themselves— and of course, the luxury of working for oneself and the benefits in financial savings (sometimes essential) make it an adventure worth pursuing many.
What Is Mixing?
Mixing refers to the final stage in the production of a single audio program— typically a song, but can also relate to a radio show, TV show, movie, commercial, webcast, or any other audio program material. In this final stage, all of the audio elements are combined to create the final version of the audio program in its intended format. Typically, that format is a stereo audio file, but it might be surround sound (requiring several files) or even mono, and it may be analog tape or some other storage media.
You are no doubt aware that most music is created from multiple sources that occupy many tracks in a typical DAW. All of these elements need to be set 2 for level, panning, and processing (EQ, compression, reverb, etc.). Mixing, thus, is creating the final placement and sound of each element over the course of the musical timeline, and then transferring the musical piece to its intended file and/or media format. The creative imagination must serve the mixer’s sonic vision of the final audio.
What Is Mastering?
Mastering most often refers to the final stage in the production of multiple audio programs—typically, a group of songs or pieces of music. In this final stage, all of the individual pieces of music, which have already been mixed down to their final format, are balanced to sound good together and a final master is created. The final master is the source to be used for duplication—for a CD this is typically a CD-R that is exactly the same as what is desired for the final CD that is to be manufactured. There is another kind of processing that refers to the creation of a single piece of audio for a particular format, such as for download from iTunes or streaming on Pandora or Spotify. This has also come to be called mastering (such as “Mastered for iTunes”), but it isn’t actually mastering in the traditional sense.
The typical rationale for changes made in the course of creating a final master that contains multiple audio files is as follows. Each element is mixed to sound as good as possible, but mixing may occur over several days, weeks, or even months yet the musical pieces will be played one right after the other on a CD or other format; all of the pieces need to be balanced for level and overall sound so that they sound good played together as a group. The first task of mastering, then, is to adjust the level of each musical piece so that they all sound like they are essentially the same volume.
Beyond that, it may be helpful to adjust the frequency balance of some songs so that they all sound relatively similar. For example, one song may sound like it has more bottom end than another. Taken individually this may not be a problem—both songs sound great—but when they are played one right after the other, one song may suffer in contrast to the other. So, the mastering engineer will adjust the low frequencies of one of the songs (more on the song that has a less low end, or less on the song that has more—or a little bit of each). It isn’t that either song really needed the adjustment if it were playing on its own, but when it’s sitting with the other songs it fits better with the adjustment. All elements of the sound: level, frequency balance, dynamic range, ambiance, and effects are considered in the mastering process.
While mastering is primarily the time when adjustments are made to provide the best compatibility between different audio materials, it may also be when the overall sound of the program material is enhanced. It can be difficult to differentiate between changes made to increase compatibility and changes made to enhance the overall sound—both considerations often enter into the final decision making.
Mastering may also be used to try to “fix” perceived problems with the mix because it is either impossible or impractical to return to the mix stage to make those changes. Clearly, because mastering occurs with material that is already mixed—typically, stereo program material— it is much more difficult to change the relationship between individual elements (this is the task of mixing). Nonetheless, it may be possible to subtly alter relationships that would be better accomplished through mixing, but can be addressed in certain ways through mastering.
Larger productions such as TV shows or movies don’t go through a separate mastering phase over the whole audio program material, though much of the processing associated with mastering may be integrated into the final mixing process, and various of the individual elements such as music cues or sound FX may get mastered separately before they go for the final mix. Music soundtracks from films released on CD and/or for download will be mastered just as any other group of music material is.
Finally, mastering is when the overall level of the program material is set. Not only does the mastering engineer set the relative level between each of the individual pieces of music, she or he must also decide on the overall level of all of the pieces (e.g., how “loud” the entire CD will be). While this was as true back in the analog days of the LP record as it is today, in the age of the CD and mp3, the issues involved in this decision have changed dramatically.
The setting of the overall program level is something that needs to be considered when mixing if the audio is not going to go to a final mastering stage. If it’s a one-off song or piece of music, then there’s no real reason for a formal mastering, but the mixing engineer will likely want to use one or more of what are traditionally mastering techniques to set the overall level of the one musical piece. Whether or not that is actually “mastering” may be debated— a master for that one element may be created as a CD-R or in some other format—but it doesn’t really fit the typical mastering process because it doesn’t bear a direct relationship to other associated material. Often, with a single piece of audio, what is created is a premaster that is a high-quality final version (including overall level processing) but that has not been converted to its final format (which would be the actual master). In many cases, the final conversion to a master is handled by the downloading or streaming service that will deliver the audio.
All of the issues touched upon here will be dealt with thoroughly in later parts of this book. This part of I introduction is intended to give those who may not have been thoroughly clear on mixing and (especially) mastering a better sense of what the roles of these functions are and where the discussion is headed.