AF’s Weblog

June 9, 2010

Audio Mastering

Tom Volpicelli of The Mastering House answers the top 10 common questions about mastering.

What is mastering and the role of the mastering engineer?


Mastering is essentially the step of audio production used to prepare mixes for the formats that are used for replication and distribution.  It is the culmination of the combined efforts from the producer, musicians, and engineers to realize the musical vision of the artist.  Each stage of the audio production process, from pre-production to mastering, builds on each other and is dependent on the previous process.  Mastering is the last opportunity to make any changes to positively affect the presentation of your music before it evolves from a studio environment to the outside world.

An awareness of the differences between the roles of mixing and mastering engineers should be noted.  While the tools may be similar, the perspectives between mixing and mastering are very different. When mixing, the focus is on the internal balance of individually recorded tracks and effects used both sonically and creatively for a single piece of music.

An album cannot be heard in its entirety until the job of a mix engineer is completed. The mastering engineer picks up where the mix engineer leaves off. Mastering is geared toward creating the balance required to make the entire album cohesive. The mastering engineer is most concerned with overall sonic and translation issues.  A mastering engineer works with the client to determine proper spacing between songs and how songs will be ordered on the CD. The flow of an album must appeal to the listener; it should engage them and take them on a musical journey as determined by the artist. Any final edits will be addressed during the mastering process as well.

Finally, the role of the mastering engineer is to provide preparation and quality control of the physical media send to the plant for replication.  This includes listening to the premaster CD to verify integrity, along with the more technical aspects such as encoding text, UPC/EAN and ISRC codes, checking for errors within the media and providing any necessary documentation such as a PQ list.

Is mastering always necessary?

A writer’s words are not complete until the editor approves them. A painter’s work is not complete until it has been matted and framed.  A musician’s work requires the same treatment. Audio production should not be rushed, finished haphazardly or completed “just to get it out there”. A finished product should reflect all of the work of the artist, producers and engineers that carry that vision forward.  Even a “perfect” mix needs mastering to a degree. In this case, you want the mastering to be as transparent as possible so that the original sound is maintained while preparing it for the final media.

As mentioned earlier, it is difficult for a mixing engineer to know how an entire album will sound in its entirety while mixing an individual track. In some cases a given track may be perfect on its own.  However, when that track is placed within the context of an album, slight adjustments in level or frequency balance may be required.  Given the amount of music distributed online, an album needs to stand out from start to finish to be noticed in such a competitive market. If the final goal is to create a product that is ready to be played on the radio, distributed online, or sold as a physical product, it should be mastered.

Mastering helps say something about the professionalism of the artist, from the arrangement of certain styles of songs to the volume of the recording to the pacing of the tracks. If an artist is serious about their music, they should make sure that someone with experience signs off on the finished product.

What kind of improvements can be expected from mastering?

Mastering can help to achieve the correct balance, volume, and depth for a style of music. It can add clarity and punch to music, giving it more vitality.  The idea behind mastering is that a product will sound better after it is treated by the mastering engineer. The degree with which a mastering engineer can achieve this is dependent on the given mixes. In some cases there may be limitations or compromises that need to be made.

One limitation of mastering is the inability to restore severely distorted material. Distortion in a mix is like corrosion; once present it cannot easily be removed and has permanently destroyed a part of the material.  While mastering can mask the effect of some types of distortion, it is essentially covering blemishes that should be addressed before the mastering stage. A common misconception is that mixes should be as “hot” as possible. With the advent of 24 bit digital technology there is no reason why mixes have to “go into the red.”

Most mastering engineers recommend a cushion of anywhere between -6 to -10 dBFS from peak level to help ensure that clipping does not take place and to allow room for processing.  In addition to peak level, the crest factor (peak-to-average ratio) is very important. While dynamic range can always easily be reduced, it is very difficult to undo the effects of over compression or limiting.

If the internal balance of a stereo mix is off, there may be compromises in the sound of the mastered track that will need to be made. For example, if cymbals or a vocal is very sibilant and bright while other parts of the mix are dark, it can be difficult to balance the overall sound in a way that enhances all elements.

In addition to frequency, levels between tracks may also be an issue. If the mastering engineer is given a stereo mix (as is usually the case) specific individual components of the mix cannot be completely isolated and processed separately.  While there are techniques such as de-essing, mid/side processing, equalizing or compressing for a specific imbalance, the results will likely not be as good as with a mix not having these issues and allowing the mastering engineer to address the balance on the whole.

One method of getting around internal balance issues is to provide alternate mixes. Some examples are vocal up/down mixes or mixes where one EQ is favored over another. Another method is supplying the mastering engineer with “stems” or sub mixes of the stereo track.  These might include a separate stereo mix of the vocals or instruments that when summed together are the same as the stereo mix minus any stereo bus processing.  In this case the mastering engineer is placed slightly in the role of a mix engineer and can make adjustments that wouldn’t be possible with a stereo mix alone. Another advantage with using stems is that alternate masters can easily be created such as radio edits, instrumental and vocal-only masters.

Another area where “fixing it in the mix” is better than “fixing it in mastering” is when dealing with the issue of noise. Mute automation on individual tracks should be used where there are noises during sections of a track that are not contributing to the mix.  Some examples are electric guitar hum/buzz on intros, outros, and breaks, bleed from headphones on the vocal track when the vocalist is not singing, drummers laying down their sticks after cymbals have faded but while other instruments are still playing at the end of a track.

Should you choose an engineer based on their “style”?

nevermindTen different mastering engineers working in the same room with the same equipment will create ten totally different masters, each sounding great on their own.  If you ask those same engineers to go back and reproduce any given master, you are likely to get ten almost identical masters back.  While each individual mastering engineer has his own style, it is important that he is able to separate himself from his style when needed.  An engineer should never let his personal taste interfere with the goal of the artist he is working with. Again, this is where communication with the client is a crucial element.

A good mastering engineer should be well versed in a variety of different categories of music. In general, there is no reason why an engineer known for creating great Country albums cannot produce a great Rock album.  While an engineer’s work should be able to transcend musical genres, if a mastering engineer has a certain style that is appealing to you as the artist, you should consider working with him.  It is important that both the engineer and the artist can communicate in a way that is complimentary to both individuals.

Which is more important, a technical background or musical one?

A mastering engineer should be well versed both technically and musically. The craft of the engineer is to be able to know good music and know how to make that music sound better.  Still, while a technical background is extremely important in the mastering world, that background should not interfere with the aesthetics.  Likewise, any personal feelings an engineer has about the stylistic choices of the music he is mastering should ultimately be discussed with the musician. It is because of this that an engineer’s musical background should not hinder his craft.

Given a technical background, some mastering engineers are capable of making modifications to equipment to create a more transparent sound, or provide color according to their taste and needs.  Having a musical background, particularly in the area of pitch, allows an engineer to identify frequency issues relating to musical notes and can speak directly to the musician about these issues in their terms.

An engineer should make sure that he strays away from favoring either background. While most engineers come from one or the other, their craft is in combining the two.  A mastering engineer should remain as objective as possible while still providing necessary feedback and insight from both a musical and technological perspective.

To read the full detailed article see:  Audio Mastering

1 Comment »

  1. Nice post thanks. Here’s some more info on Audio Mastering

    Comment by platinumdave — December 19, 2010 @ 11:42 pm


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