BASICS OF 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). In recent years digital masters have become usual, although analog masters—such as audio tapes—are still being used by the manufacturing industry, particularly by a few engineers who specialize in analog mastering.[citation needed]
Mastering requires critical listening; however, software tools exist to facilitate the process. Results depend upon the intent of the engineer, the skills of the engineer, the accuracy of the speaker monitors, and the listening environment. Mastering engineers often apply equalization and dynamic range compression in order to optimize sound translation on all playback systems.[1] It is standard practice to make a copy of a master recording—known as a safety copy—in case the master is lost, damaged or stolen.
The source material, ideally at the original resolution, is processed using equalization, compression, limiting and other processes. Additional operations, such as editing, specifying the gaps between tracks, adjusting level, fading in and out, noise reduction and other signal restoration and enhancement processes can also be applied as part of the mastering stage.[7] The source material is put in the proper order, commonly referred to as assembly (or 'track') sequencing. These operations prepare the music for either digital or analog, e.g. vinyl, replication.
If the material is destined for vinyl release, additional processing, such as dynamic range reduction or frequency-dependent stereo–to–mono fold-down and equalization may be applied to compensate for the limitations of that medium. For compact disc release, start of track, end of track, and indexes are defined for playback navigation along with International Standard Recording Code (ISRC) and other information necessary to replicate a CD. Vinyl LP and cassettes have their own pre-duplication requirements for a finished master. Subsequently, it is rendered either to a physical medium, such as a CD-R or DVD-R, or to computer files, such as a Disc Description Protocol (DDP) file set or an ISO image. Regardless of what delivery method is chosen, the replicator factory 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 the following:
- Transferring the recorded audio tracks into the Digital Audio Workstation (DAW)
- Sequence the separate songs or tracks as they will appear on the final release
- Adjust the length of the silence between songs
- Process or sweeten audio to maximize the sound quality for the intended medium (e.g. applying specific EQ for vinyl)
- Transfer the audio to the final master format (CD-ROM, half-inch reel tape, PCM 1630 U-matic tape, etc.)
Examples of possible actions taken during mastering:[7]
- Editing minor flaws
- Applying noise reduction to eliminate clicks, dropouts, hum and hiss
- Adjusting stereo width
- Equalize audio across tracks for the purpose of optimized frequency distribution
- Adjust volume
- Dynamic range compression or expansion
- Peak limit
- Inserting ISRC codes and CD text
- Arranging tracks in their final sequential order
- Fading out the ending of each song (if required)
- Dither
