What is Mastering?
Mastering adds the final sonic touch to a mixed song. It is the final process performed on a song before it gets released and distributed. Mastering aims to address the following issues
1. Matching a song's sonic character to that of other songs on the same album or sequence, so listening to them in sequence feels natural.
2. Optimizing loudness, so the song doesn't sound softer than other songs that might be played before or after it.
3. Adding the last touch of sonic enhancement to the mixed song, addressing macro problems such as harshness, muddiness or lopsided stereo balance, and complementing the mix with subtle global adjustments to EQ, clarity, warmth, punch and wideness.
Mastering is a quicker process than mixing and makes less of a difference on the overall sound of your song than mixing, but is nonetheless important as a finishing touch after mixing. It polishes the final mix so all the elements sound as good or better, while achieving extra loudness and 'glue'. Mastering is the final bridge between the mix and distribution.
No two mastering jobs are the same. The nuances of the source material make all the difference in how the engineer approaches mastering, and different engineers have different styles. Engineers may need to merely fine-tune a recording before it's ready to be distributed. Other times, a mix might require a significant amount of cleaning up. Regardless of the project, the goal of mastering remains the same: to ensure audio sounds great across multiple platforms and on different speakers. Mastering is as much a creative art as it is a science and is just as important as other elements in the production process. Get it wrong, and your listeners might think a track sounds "too loud and harsh" or "too muffled or weak" Get it right, and assuming the production and mix are good, your listeners will enjoy the experience.
Different Mastering Techniques
There are various techniques involved in audio mastering. Engineers might use some or all of the following:
Compression and limiting: Compressors and Limiters reduce the dynamic range of the final mix, and when used with taste, make the mix sound fuller, louder and more cohesive. It's easy to squash a mix with poor use of compressors and limiters so you want to work with an engineer who has experience, a good listening environment, a great set of ears and good gear.
Clipping: Some mastering engineers push their A to D converters or use software clippers to subtly lop off the peaks of an audio file, to achieve increased perceived loudness.
Equalization: Optimizing for a sonic balance that complements the song, often described in adjectives such warmth, huge bottom, brightness, openness or airiness.
Sequencing and spacing: If you are mastering an entire album, spacing lets you determine the amount of silence between each track, sequencing of their order, and fades during song endings.
Creative Effects: Other effects include subtle reverb on the whole mix, distortion, stereo widener or filters.
Restoration: This process gets rid of any issues or unwanted sounds, such as pops, clicks, hum, and hiss.
Preparation for distribution: Some engineers will prepare audio files based on particular specifications of online music stores and streaming websites such as iTunes, Spotify, Apple Music, or CDs. This might entail adjusting the file format, bit rate, sample rate and metadata depending on your needs, and the platform you are distributing to. Other mastering engineers deliver a high resolution Wave file is often sufficient based on your needs.
How to Choose a Mastering Engineer
Not all mastering engineers are the same. Some important factors to consider when choosing an engineer are experience, gear, listening environment and specialization in a particular genre. There are some benefits to choosing an engineer who has mastered recordings in your genre. Listen to examples of his or her work. This gives you a feel for their work and lets you decide whether an engineer is right for you. Do they specialize in mastering? It might be fine that they do other things, as long as they are devoted enough to the art and science of mastering to have the proper gear, a well tuned critical listening environment and experience.
On SoundBetter you can listen to sound samples, research a mastering engineer's experience, and read reviews of previous clients.
Keep in mind that while the most renowned sound engineers might charge thousands of dollars for their services, some offer reduced rates to indie artists and producers. Also, some engineers might charge you less if you pay for several songs or an entire album in advance. Keep in mind that mastering is a relatively affordable step in the process, so probably not worth skimping on.
How to Prep Your Mixes for Mastering
The first step of preparing a mix for mastering, is to be sure you love the mix. Don't expect mastering to fix a mix you don't love.
Once you are happy with the mix, simply export the tracks to a stereo file from your DAW (Digital Audio Workstation), with the same sample rate and bitrate as your original mix session. If it's 16/44.1, use that. Same goes for 24/48, and so on. Don't upsample (export from a lower to a higher sample rate).
This is probably the most critical piece of advice when sending a song for mastering - Make sure there is headroom. In other words pay attention that you aren't clipping or regularly peaking your master bus. The mastering engineer needs some room to manipulate the audio file. A mix that is very 'hot' doesn't leave them that room. One of the biggest pet peeves shared by engineers is audio mixes that are too loud. These recordings are difficult to master and might result in a finished product that sounds very similar to the final mix. -3 dB of headroom is usually fine, but the rule of thumb is simply make sure the mastering engineer has headroom to do their work.
If you have any plugins on your master bus, you can remove them, unless they are creative effects that are integral to the production. Generally speaking compressors, EQs and limiters should be removed. If this causes your track to clip you can just pull your master fader back a bit, or leave a limiter on, but set it to no gain reduction - rather just to catch the few peaks, so you don't clip the DAW's master bus. If you do leave a limiter on, make sure you have dither set to 'off'. If you see the limiter is gain reducing a lot, even though you didn't set it to gain reduce (i.e you set it to 0 or -.01), that means you're hitting the input of the master bus too hot, and you should pull back the faders on your individual tracks. If you do need to pull all your individual tracks down by a couple of dB, make sure you account for tracks that have automation written as they may 'bounce back' to their original position. You can avoid this by lowering all the tracks through the automation, rather than using the faders.
Make sure you review your mix to remove any pops or clicks. You may not notice these but if they exist they may be accentuated in mastering. It's helpful to listen to individual tracks soloed to catch these. Pay particular attention to where you have edits. If you didn't fade edits, you might have digital pops that are easy to miss when many tracks are playing together, but that should be addressed.
Lastly, align your expectations. Some clients expect too much from mastering. There are subtle things that can be done in mastering to shape and optimize loudness, tone, punch and intensity. However mastering is not mixing. Mastering can only slightly improve a mix. It doesn't replace the need for a great recording, production and mix. Those are the ingredients that make all the difference. Mastering is just the cherry on top.
Master your songs
Mastering is best left to professional mastering engineers. It is affordable enough, that squeezing 5% more shine out of your track, as opposed to reducing the quality by 5% by not working with a pro mastering engineer, is usually a good investment after you've put in all the work to get to that point. Prepping your mixes for mastering and hiring a great engineer with experience in your genre could provide you with just the right touch to take your track from great to awesome. Do remember though, that a mastering engineer can shine a diamond, but not create one.