Many musicians nowadays record and mix their own material. This has allowed for an explosion of new music on the landscape. Creatively, there is a great deal of diversity in musical styles and expression, which is great, but unfortunately, there is also a large variation in the quality of recordings. While it is true that generally the production quality of what DIY musicians create has increased dramatically in recent years (due to the availability and low cost of advanced technology), there is often less attention paid to the important final step in the traditional production process. I am referring to the practice of mastering.In this article, I will attempt to outline some essentials of mastering that will hopefully apply to a wide range of musical styles and genres.
The intention is not to be a comprehensive guide to mastering. We will, instead, focus on the basics of mastering to give a general understanding of the processes involved. It is important to note that we will be discussing mastering where the ultimate distribution format is a digital file such as .WAV or .AIF.
In The Mastering Engineer’s Handbook, Bobby Owsinski defines mastering as ’……the process of turning a collection of songs into a record by making them sound like they belong together in tone, volume, and timing (spacing between songs).’ Mastering can also be defined as the final process of alteration and verification with the purpose of preparing the audio material for a distribution format. The process often involves enhancements made to the dynamic, spectrum and panorama parameters of the mix. In other words, loudness, frequency distribution and stereo width of the mix can be (and usually are) altered to achieve a more refined final product that is in line with modern industry practice.
First, let me say that if you can, get somebody else to do the mastering for you –– especially if you are the person that recorded and mixed the track. This is to ensure a fresh pair of ears listens to the mix without any carryover effect from the mix down process. If however, you are not in the position to send your tracks to a mastering engineer, read on.
One of the most important tips before you begin mastering is to allow time between mixing and mastering. This lessens the degree to which you are invested in the mix and think as the mixing engineer. I would say give it at least a couple of weeks.
Before starting, I recommend sitting down and listening through the tracks and making notes about what bothers you most about the mixes. These notes need to be as specific as possible. Listen to the frequency balance, dynamics, stereo width and pay special attention to any unwanted noise or distortion. This should also be the time when you decide on the sound you are going for. Do this by putting together a playlist consisting of a few tracks of similar genre that you think are of good enough quality to act as your reference tracks.
The tools for mastering include (usually high quality) equalisers, compressors, stereo enhancers, noise reduction processors and limiters. Modern DAWs (Digital Audio Workstations) include most of these as standard plug ins, but you could also spend some money on specialised plug ins that might not be included in your DAW, or that might be of higher sonic quality.
One of the most profound ways of affecting a track is to change its frequency balance with an equaliser. When EQing, consider using small adjustments across a range of frequencies rather than a large amount of EQ applied at a single frequency. Think about reducing frequency ranges that you dislike rather than boosting the frequencies that you do like. In general restraint is the key here. It might be tempting to adjust EQ by 10dB or 15dB, but try to limit the amount of EQ to within a range of 3dB or so. Needing to use excessive amount of EQ can be indicative of serious problems with the mix.
Compression is another essential process used in mastering. Remember, a compressor reduces the difference between the loudest and quietest levels by decreasing the loud signals and increasing the quiet ones. For more information about compression you can refer to Reuben Rowntree’s article in the December, 2014 (Vol. 18, No. 7) issue of NZM.
When compressing, it is better to underdo than to overdo it. Owsinski elucidates: …’…generally speaking, the trick with compression in mastering is to use a slow release and less (usually much less) than 5dB of compression”. And “……quiet passages that are too loud and noisy are usually a giveaway that you are seriously over-compressing.’ Use lower ratios of 1.5:1 to 3:1 and avoid using ultra fast attack times, favouring slower attack and release times for transparent compression. Oh, and do not use normalisation, it does more harm than good.
Another widely used process in mastering is stereo enhancement. This is the process by which the stereo width of the track is increased by adding some out-of-phase components from one channel to another. Increasing the stereo width can improve definition of instruments by giving them a bit more space to sit in. However, be careful when adding stereo enhancement as too much of the out-of-phase content can severely compromise mono compatibility and can create an ambiguous and weak middle image. As a rule of thumb, try to limit the amount of stereo enhancement to no more than 30%.
The final step in mastering has traditionally involved the use of a limiter, with the goal of increasing the perceived loudness of the track at the expense of its dynamic range, and limiting the absolute peak level of the audio material.
In digital audio there is an absolute restriction of how hot (in terms of level) a track can be. If this ceiling is exceeded, the result will be inharmonic and unpleasant distortion. By setting a limiter correctly at the end of the chain, it becomes possible to control the peaks in the program material so that they do not exceed the ceiling. Overuse of limiters has led to a phenomenon commonly known as the ‘Loudness War’.
Loudness War refers to the tendency of making tracks loud by reducing the peak content of the material while increasing its average amplitude. When overdone (unfortunately, too often the case), this can cause tracks to lose definition and impact. With announcements from iTunes radio, Spotify and even YouTube, that they are now adjusting the playback level of the tracks to a set amount, we can maybe regard the loudness war as a thing of the past. If a streamed track is louder than this set value, then the track will be turned down and if the level is too quiet, it will be turned up. So, it is no longer advantageous to sacrifice the dynamics of a piece of music for loudness. (Was it ever advantageous?) With this in mind, use limiting judiciously and aim for the average dynamic range of 8dB to 14dB.
Mastering should be a process of subtle adjustment of a variety of parameters with the aim of creating smoother sound all the while maintaining the context and cohesion between the tracks. There is far more to this art than I have mentioned here. If you are interested in finding out more, there are great resources that come highly recommended. Books such as The Mastering Engineer’s Handbook by Bobby Owsinski and Mastering Audio by Bob Katz should get you on your way to achieving sonic excellence. And, of course, the best way to learn these types of things is by practice.
David Chechelashvili is a tutor at SAE Institute and a studio and mastering engineer. In his spare time he composes ambient music and collects synthesisers. He can be contacted at email@example.com