Audio Mastering - Process

Process

The source material, ideally at the original resolution, is processed using equalization, compression, limiting, noise reduction and other processes. 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. This step prepares the music for either digital or analog, e.g. vinyl, replication. The source material is put in the proper order, commonly referred to as assembly (or 'track') sequencing.

If the material is destined for vinyl release, additional processing, such as dynamic range reduction, frequency dependent stereo–to–mono fold-down and equalization, may be applied to compensate for the limitations of that medium. Finally, for compact disc release, Start of Track, End of Track, and Indexes are defined for disc navigation. Subsequently, it is rendered either to a physical medium, such as a CD-R or DVD-R, or to computer files, such as a DDP file set or an ISO file. 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. Regardless of what delivery method is chosen, the replicator will transfer the audio to a glass master that will generate metal stampers for replication.

The process of audio mastering varies depending on the specific needs of the audio to be processed. 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.

Steps of the process typically include but are not limited to the following:

1. Transferring the recorded audio tracks into the Digital Audio Workstation (DAW) (optional).
2. Sequence the separate songs or tracks (the spaces in between) as they will appear on the final release.
3. Process or "sweeten" audio to maximize the sound quality for its particular medium (e.g. applying specific EQ for vinyl)
4. Transfer the audio to the final master format (i.e., CD-ROM, half-inch reel tape, PCM 1630 U-matic tape, etc.).

Examples of possible actions taken during mastering:

1. Editing minor flaws
2. Applying noise reduction to eliminate clicks, dropouts, hum and hiss
3. Adjusting stereo width
4. Adding ambience
5. Equalize audio across tracks
6. Adjust volume
7. Dynamic range expansion or compression
8. Peak limit

To finish mastering a CD the track markers must be inserted along with ISRC, PQ codes, text and other information necessary to replicate a CD. Vinyl LP and cassettes have their own pre-duplication requirements for a finished master.