Mastering, a form of music or audio post-production, is the process of preparing and transferring recorded audio from a source containing the final mix to a data storage device (the master); the source from which all copies such as audio CD swill be produced (via methods such as pressing, duplication or replication).
This cohesive audio program, in a tonal context, is fine tuned through equalization and audio level compression. More tasks such as editing, pre-gapping, leveling, fading in and out, noise reduction and other signal restoration and enhancement processes can be applied as part of the mastering stage. Program material is also usually put in the proper order at this stage.This is commonly called the assembly.
The specific medium varies, depending on the intended release format of the final product. For digital audio releases, there is more than one possible master medium, chosen based on replication factory requirements and/or record label security concerns.
A mastering engineer may be required to take other steps, such as the creation of a PMCD (Pre Mastered Compact Disc), where this cohesive material needs to be transferred to a master disc for mass replication. A good architecture of the PMCD is crucial for a successful transfer to a glass master that will generate stampers for reproduction.
The process of audio mastering varies depending on the specific needs of the audio to be processed. Steps of the process typically include but are not limited to:
Transferring the recorded audio tracks into the Digital Audio Workstation (DAW) (optional).
Sequence the separate songs or tracks (The spaces in between) as it will appear on the final product (for example, an Audio CD).
Process or (sweeten) audio to maximize the sound quality for its particular medium.
Transfer the audio to the final master format (i.e., Red Book compatible audio CD or a CD-Rom data, 1/2" reel tape, PCM 1630 U-matic tape, etc.).
Examples of professional audio music CD mastering actions taken:
Adjust volumes.
Edit minor flaws.
Apply noise reduction to eliminate hum and hiss.
Peak limit the tracks.
Dynamic compression.
Dynamic expansion.
Adjust stereo "width".
Add ambience.
Equalize audio between tracks.
The guidelines above are mainly descriptive of the mastering process and not considered specific instructions that may or may not be applied in a given situation. Mastering engineers need to examine the types of input media, the expectations of the source producer or recipient, the limitations of the end medium and process the subject accordingly, which is why it pays to consult and expert in the field of Audio CD Mastering like Elliott Federman!