Mastering is the final step in the process of finalising an audio production. It is a key step in providing a quality piece of work. It's a bit like adding some photoshop, where you edit bits and pieces in and out to provide the best overall output. with the help of several audio tools. These small differences will make the difference between good and excellent productions. Although every engineer will resort to different methods of processing audio to obtain satisfactory result, the tools used are usually the same; EQ, compression, limiting and so on. Mastering must not be confused with overall mixing. The first is a process applied on the final track, while mixing involves applying a similar process, but on individual tracks within the audio production.
Mastering starts off by opening your final mix inside a DAW, or Digital Audio Workstation. While Pro Tools is the most common DAW for mastering, other powerful softwares such as SADiE, Pyramix, are also available. The choice of DAW is personal to every engineer. “Silence” between tracks are edited, due to CD players taking a small amount of time to unmute when moving on to another track, a gap of 300ms of silence at the start of a track is preferrable to avoid lost transients.
The next stage is the most important and time consuming. It is the dynamic processing or “sweetening” of the audio to maximise the sound quality. This is done using the processing tools mentioned earlier. Equalization is applied in small amounts to balance the track. It is important that each frequency band is balanced with the rest so that they are complimenting each other rather than fighting for space. Compression is used to add punch and warmth to the mix as well as loudness. In mastering, a Multiband Compressor will be used. It does the same job as an ordinary compressor however it allows the engineer to compress sections of the frequency spectrum which makes it all the more accurate and efficient. Limiting will allow the loudness to be pushed further without peaking or clipping. Compression and limiting must be used in moderation, an overly compressed track that has been pushed too far will be left with a small dynamic range, making it sound flat and dull. The final stage in the “sweetening” chain is Dithering which is simply the application of a low level random noise if the audio is truncated. Truncation describes the reduction in resolution of audio i.e. from 24-bit to 16-bit. When this happens, the sound quality is diminished as the extra 8 bits are lost. By adding random noise, it helps in masking the distortion produced by truncation, making the many short-term errors much less noticeable to the listener. This is a very powerful tool should always be applied before truncation!
Once all of these steps are complete and both parties are happy, the final master can then be transferred to the final format (CD-ROM, half-inch reel tape, PCM 1630 U-matic tape, etc.) From this the song or songs can then be duplicated.
The success of mastering relies heavily on the monitoring and listening environment in which it was mastered. The better the speakers, the more detail is heard therefore the greater the accuracy. This goes for the processing tools used as well, professional standard EQ, compression and limiting help greatly in achieving a finer sound. This is why a professional recording studio set up is desirable. Mastering can be thought as the final push in highlighting what's great about a track or album. By carrying out each step correctly, it can make a good piece of audio into something well polished, professional sounding and marketable!