What Is Mastering?

Mastering, a form of 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 will be produced (via methods such as pressing, duplication or replication). The format of choice these days is digital masters although analog masters, such as audio tapes, are still being used by the manufacturing industry and a few engineers who have specialized themselves in analog mastering.

The source material is processed using equalization, compression, limiting, noise reduction and other processes. Subsequently, it is rendered to a medium such as CD or DVD. This mastered source material is also put in the proper order at this stage. This is commonly called the assembly or track sequencing. More tasks such as editing, pre-gapping, leveling, fading in and out, and other signal restoration and enhancement processes can be applied as part of the mastering stage.

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 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 the following:

•Transferring the recorded audio tracks into the Digital Audio Workstation (DAW) (optional).
Sequence the separate songs or tracks (the spaces in between) as they 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, half-inch reel tape, PCM 1630 U-matic tape, etc.).

Examples of possible actions taken during mastering:
•Edit minor flaws.
•Apply noise reduction to eliminate hum and hiss.
•Adjust stereo width.
•Add ambience.
•Equalize audio between tracks.
•Adjust volumes.
•Dynamic expansion.
•Dynamic compression.
•Peak limit the tracks.

The guidelines above are mainly descriptive of the mastering process and not considered specific instructions applicable 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. General rules of thumb can rarely be applied.

(from wikipedia)

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