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I have written several short articles on and related to the subject of Mastering that have been published on various websites. I'm including them here in hopes you will find them useful.

About Audio Mastering and Music

Professional Music Mastering is first and foremost a decision-making process and then it's about making key and specific changes to the sound.

Mastering has been around longer than some realize. Even vinyl records were (and still are) mastered as part of the pressing process and include procedures to ensure audio signals conformed to the limitations of vinyl. With the advent of digital systems, mastering has become more of a household name and becomes even more of a sonic challenge as digital recording advances and demands for better sound increases.

You can think of a Mastering Engineer as an over-and-above producer. The Mastering Engineer comes in at the end of a recording project and makes key decisions and suggestions on the overall sound and layout that will be presented on an album. Artists, Producers and Labels alike rely on the Mastering Engineer to ensure that they release the best-possible sounding album with maximum impact. For this reason, a Mastering Engineer needs more than just experience in audio engineering - experience in other aspects of the entertainment industry is vital as well. The Mastering Engineer is after all, the last person to 'judge' and make changes to a project that may cost many thousands of dollars.

Besides a good ear, a Mastering Engineer must also possess a knowledge of what works and what doesn't work in the sonic realm, a good understanding and feel for different genres of music, a good grasp of how to make an album 'flow' from the first to last track and much more. Professional mastering requires a certain level of experience, knowledge and discipline. Like any specialized field, there are no shortcuts, it simply takes time and dedication to develop the necessary skills.

A part of the concept behind mastering is to give a project one final 'look over', by someone with audio experience who has not heard the material before. Usually by the time a mixing engineer or producer has completed mixing a project, they have heard the songs so many times that it is very hard to listen objectively. It is mainly for this reason that mastering on major-release albums is almost never performed by the same person(s) doing the mixing or producing. In most cases the producer, audio engineer, etc. do not even attend mastering sessions unless they have particular concerns or changes in mind. They will trust the Mastering Engineer's suggestions and decisions.

Mastering Engineers should also have the ability to develop excellent relations with their clients and not have problems discussing changes with the people involved in the making of an album. Professional Mastering Engineers must tell their client(s) immediately, if they feel something is wrong with a particular mix or take. Sometimes tracks are referred back to the producer or mixing engineer for changes. An honest and open relationship with that producer or engineer is essential.

Finally, mastering is not so much about gear and software, as it is about the ear and judgment. Major labels and producers expect and demand their 'product' to have the utmost sonic appeal to the broadest audience possible. Only many years of study and experience can prepare an audio engineer for that responsibility.

Pre-Mastering Tips for a Better Album

Here are some tips you can follow before sending your project to a mastering facility. Although the items discussed here do not cover all scenarios, following these tips will help ensure that you get off to a good start and get the absolute best results from your mastering facility.

- Preparing files for your mastering engineer.

- Should I compress and/or limit my stereo mix?

- Should I not at least normalize the files?

- Using stereo effects.

- What about CD TEXT?

Preparing files for your mastering engineer.

You should obviously check with your Mastering Engineer (ME) on acceptable formats, but in most cases you will be asked to keep your files in the highest possible resolution in either WAV or AIFF format 'data' files. Quite frankly, if your ME tells you to send an 'audio' CD as your master, leave that mastering facility and find another - fast!

If you recorded your project at 24-bit, 96 kHz, render your mix to that same resolution without applying any dithering. Don't render your files to 16-bit, 44,1 kHz simply because it's going to end up in that format (Red Book). 24-bit files leave more headroom for the mastering process. Dithering should always be left as the absolute last process, which is usually your ME's responsibility. Most mainstream audio editing software will give you the option to dither or not when you render (export) your mixes to files. This might sound absurd, but it has happened - never render or export your files to a resolution higher than they were recorded. 

Do not trim the beginning and ending of your files, leave everything intact. Most ME's have the experience and 'feel' to help you make your album 'flow' and might often suggest different fade positions, lengths, etc. If you have very specific ideas or requirements on how you want your album to flow, you should send a set of notes with the files to explain where you want your songs to start, end, fade, etc. It might even be a good idea to send a reference CD of your fades, etc. with the job. Another reason for not trimming your files relates to noise. If you need noise removed from the recording, a good 'clean' sample of that noise can be very useful.

Don't write your files to CD using the highest burning speed available to you. Up to around 8x speed is reliable in most cases, but 2x is preferred. If your CD/DVD burning software has the option to 'verify written data', use it. Nero Burning ROM for instance has this option. You don't want to send your CD halfway around the world only to find out that some data on it contains errors or are inaccessible. If you're not sure how to check your CD, try copying the CD contents back to your own system, open the files and make sure they are what you expect them to be.

Should I compress and/or limit my stereo mix?

I know we are all tempted to compress our stereo mixes so they sound really tight and punchy. While that approach to mixing is perfectly normal, we are all guilty of over-compressing a mix at least once in our lives. Over-compression causes a lot of problems in a mastering facility.

First of all, compression is one of those things which, once in a mix, can not be removed or fixed satisfactorily. I experience compression as the biggest problem with mixes sent to me. Sometimes I receive mixes (which are totally over-compressed) with a note from the sender: "Please make it sound loud, but not over-compressed". This just reemphasizes to me that many audio engineers don't know how to use compression or limiting properly, especially on the stereo mix. Coupled with the 'mix to master' syndrome happening in many studios today, that can only mean one thing - more 'bad' mixes are hitting the road than ever before.

So what can be done about this? You need your mixes to sound great and also get rid of the transients and spikes in your mixes, right? Well, the answer is quite simple really, in fact many professional studios follow this method. Render two mixes, one with your compression and limiting and one without. The mix without not only becomes the copy you send to your mastering facility, but also an important 'unaffected' back-up copy. If you later find your mix sounds too compressed, you can simply reload the unaffected version and try different compression and limiting settings.

Your ME should be experienced enough to know exactly how much compression and/or limiting is needed to preserve the dynamics for your particular genre of music. The ME will also know how much room to leave to compensate for the 'ugly' compression/limiting applied by radio stations in general.

Should I not at least normalize the files?

No!

Using stereo effects effectively.

Another bad thing that can happen to an overall mix is the improper application of stereo enhancement effects. Stereo enhancers, when used wrong, will just make your mix sound sloppy and 'un-tight'. They can also cause phasing (bad sound) problems, even when used on individual tracks. The rule of thumb to avoid this problem is - never use stereo enhancers on a mix heading for mastering.

When a ME listens to the overall flow of your album from start to finish, he/she will know where and where not to enhance the stereo image of each song. In some cases the ME might even narrow the mix to better fit the overall project.

What about CD TEXT?

Although CD-Text is not strictly Red Book format, this feature has become quite popular since the arrival of CD players that can display this information.

If you want to include CD-Text, be sure to inform your ME and send a printed copy with the names of the songs, the artist for each song (if different from song to song) and the album title. All these should be checked for typos like capitalization, spelling and grammar. If you have a weird way of spelling certain words like using 'da' instead of 'the' for instance, make a note of that to the ME.

The 'Loudness' Factor and Musicality

If you regard the musicality side of music creation as unimportant, this article will most likely not appeal to you.

There has been much talk in magazines and online about the ‘loudness’ factor in mastering. This is also known as Root Mean Square (RMS) and refers to the average ‘loudness’ of audio. Something that kind of amazes me is that producers, musicians, labels and studios will spend thousands of dollars creating music and then end up over-compressing and limiting the wits out of it in the final stages. This is supposedly done to be more ‘acceptable’ to radio stations and the public listener. But is it really that acceptable?

I can honestly say that since my first days as a Mastering Engineer, my views on this subject have never changed. I’ll express them and my assessment on ‘loudness’ from two angles.  What does it do to the music?  What does it mean to you and your listeners?

What does it do to the music?

Take a look at these 2 figures of a very small portion of the same audio clip. Fig.1 is what an over-compressed and limited wave looks like when zoomed in (and I have seen worse). Fig.2 is of the same wave with just the right amount of compression and limiting. These two waves have the same perceived ‘loudness’, but the one in Fig.1 does not sound as open and transparent as the one in Fig.2.

The amplitude represented vertically on these charts is also, an almost direct representation of speaker movement. In effect, the speaker diaphragm does not move when it gets to the sections indicated by the arrows in Fig.1. These are what I call ‘tabletop’ waves - the wave hits digital zero and stays there for very small fractions of a second and so does the speaker diaphragm. This can also be called ‘mechanical distortion' and will contribute to the condition known as 'ear fatigue'. The wave in Fig.2 on the other hand allows for continuous speaker movement and does not cause distortion. The sound in Fig.2 is much clearer, instruments stand out better and the stereo image is more defined.

I may not be very popular among some of my colleagues for saying the following, but it’s easier to end up with a Fig.1 type wave on analog equipment than on digital equipment. Most digital mastering stations apply a ‘look ahead’ type compression and limiting and will make the necessary adjustments internally to prevent ‘tabletop’ waves. Please understand, the majority of analog mastered albums by industry professionals sound great because these guys and gals know what they are doing. The problem occurs with the relative newcomer to this field and I believe everyone should know what to look out for when having their albums mastered.

What does it mean to you and your listeners?

Ever wondered why many songs don't sound so open and transparent on the radio? Besides the obvious limitations of radio signals, the other contributing factor is that almost all radio stations (many of them will deny it) compress and limit the signal that goes out on their transmitters to make the sound louder. Now, imagine our poor overly compressed and limited wave in Fig.1 being compressed and limited even further - the result speaks for itself. Classical stations for the most part, also compress and limit their signals, but they do so at moderate to low levels. Even if you’re not classical music fan, dial in a classical station sometime and you’ll hear how much better the 'sound' is.

You've heard the saying - "Sometimes less is more". It applies here. Audio material that is mastered less ‘hot’ (and we’re talking just 1 or 2 dB’s) simply sounds much better regardless of the format - on a CD, on the radio or when turned into MP3 or WMA files. The music becomes more 'musical'. Perhaps the greatest benefit of this approach is that due to less 'ear fatigue', your audience will be able to listen to your music longer. What musician doesn't want that?

I talk with many of my clients about the ‘loudness’ factor in music, but in the end it is their decisions that matter to me and my input only serves as a recommendation.