Mastering is simple. And hard.
In this post, I’ll talk about the general process of mastering, and some specifics about what we’ve learned about how to master effectively in iZotope Ozone. We’re not experts by any means, but we think our experience can help others who are looking to do lightweight mastering of their own work.
What is mastering?
Simply put, mastering is the process of taking final mixed recordings and preparing them for distribution and airplay. The goals of mastering are to make the final recording sound as good as it can on the widest variety of music systems. Additionally, mastering sets the average and peak levels of the music to standard values so that they are comparable to other recordings they’ll be combined with in a set or playlist. Finally, mastering can be used to address flaws in the source recording by modifying the EQ profile, applying compression, or by exposing or hiding frequency bands that may be under-or over- represented in the track.
For a more detailed look, see the following articles. There’s lots more to read about mastering, but the following two articles are a good introduction:
Working the tradeoffs between “loudness” and dynamic range
One of the things that people look to mastering to do is to maximize the average volume of a track. This makes it sound as loud as possible throughout the track. This means that it will cut through the noise in the club, pop more on the radio, and so forth. However, “louder” might not be right for all types of music.
At a high level, mastering tools perform two distinct operations to make a track sound louder:
- Reducing the volume difference between the loudest and softest sounds (compression)
- Truncating the hottest peaks to allow increasing overall volume without producing clipping (peak limiting)
Here’s some examples, using our track April’s Rock Sandwich. I chose this track because it has a reasonable amount of dynamic range, while still being fairly consistent throughout the track.
Here’s what the waveform of the rough mix looks like in Audacity:
Notice that there’s a good amount of dynamic range between the average signal and the peaks: the waveform looks spiky like a comb. Also notice that in the mixing process, we left a solid amount of headroom above the peaks, so there’s no question of clipping.
Here’s the track in iZotope Ozone. For this first example, I’ve set Ozone to compress to K-12 (12DB maximum delta between average and peak level), and set the limiting threshold quite low. This is not how we typically master our finished tracks, but it will serve to demonstrate how to maximize loudness.
The second waveform in the screenshot above shows how the maximizer is responding to peaks in the music by drastically reducing the peak levels in order to smooth out the volume profile of the track.
The result is a track that is consistently loud from end to end. Here’s the resulting output in Audacity:
Listening to the track, it sounds loud, it sounds consistent, and there’s no clipping. This is how a lot of pop music – particularly EDM – is mastered. It’s a wall of volume.
What’s missing, though, is dynamic range and a feeling of space. In the original track, the transients in the guitar pop out, and the cracking sounds of the duct tape that we sampled to use as percussive elements are subtle elements that you notice if you listen intently. There’s clean separation of the instruments, and a sense of space. There’s a certain amount of rise and fall of volume and overall energy between adjacent sections of the track. The space and separation are lost to compression, along with the dynamic range.
Because our music is complex, with multiple musical voices and a variety of timbres, some subtle and some less so, we value the sense of space and dynamic range which allow the subtlety to be heard. So, we prefer a lighter touch in mastering. Here’s a more typical approach to mastering a Cats Cradle Robbers track, still using April’s Rock Sandwich:
In this screenshot, you can see that we’re still using just the Maximizer, but in this case, I’ve left the default limiting threshold, and adjusted the volume so that we’re just barely hitting the peaks of the hottest transients. In addition, I’ve set the I/O scale to K-14 to allow a broader dynamic range between average and peak levels.
The result is a track that has a good hot level, but still has enough dynamic range to allow the individual instruments to be heard distinctly. I can hear that mix that we worked so hard to get.
Our tools and approach
Here are the specific tools, systems, and workflows we’re using for mastering today:
iZotope Ozone 7
While it’s possible to build your own mastering chain from individual plugins, we find the ease and power of iZotope’s mastering solution to be everything we need and more. We’ve used Ozone for 4 out of 5 of our albums to date.
When using Ozone, we try to adhere to the following principles:
- Use K-14 metering. We’ve standardized on the K-system of metering, and we’ve decided to use K-14 because it allows us to pump up our tracks to a decent volume, while still allowing a good amount of dynamic range. If your music is simple and you value volume over subtlety, try the more aggressive K-12, or use a different metering approach. Here’s a good introduction to the Katz (K) metering system: http://www.meterplugs.com/blog/2016/10/14/k-system-metering-101.html.
- Master using the standalone app. Since all of the Ozone plugins are supplied as VSTs, it’s possible to use them in your DAW of choice (we use Ableton Live), either on individual tracks or on the master output. However, we prefer to provide a clean separation between mixing and mastering. We work in Ableton to create the best mix possible, and only when we think we have a mix worth shipping do we pull it into the Ozone app.
- Use the simplest possible chain. The Ozone plugins are extremely powerful, and each one can deeply affect the sound of the finished track. Different plugins can help emphasize or minimize various frequency bands, and either enhance or erode your mix. After a lot of experimentation, we’ve fallen back to a “light touch” mastering approach. For Every Kitty Dance Meow, we used only the Maximizer, set to the “Classic Master” preset, and we modified only the input gain, raising the track volume with the goal of having the average track volume at 0db, and only the highest peaks touched by the limiter. NOTE: simply having the plugins in your mastering chain will change the sound of your track, even if you leave them in default configuration, so we recommend removing anything you’re not planning to use. We typically use only the Maximizer, which means we need to remove the default Equalizer and Dynamics that Ozone adds when we start mastering a new track.
- Don’t change it in mastering if you can help it. In most cases, if we were tempted to make deeper changes (such as adding static or dynamic EQ to emphasize or minimize a given instrument), we wound up revisiting the mix instead so that we could make only the surgical change desired. Most mastering engineers only have access to the final stereo mix, but if you have the ability to change the mix in response to issues found during mastering, it’s often a better way to achieve your ends. Mastering can help brighten the overall sound of a mix, for example, but it’s not the best way to get your bass to pop out if the bass is simply too low in the mix, or if what you really need is to deal with frequency collisions or add sidechain compression. If you do use additional plugins, use a light touch. Even small changes can have big impacts on the music.
Is the future of mastering in the cloud?
As the indie music market grows, the opportunity to master online grows as well. A web search for online mastering pulls up a bottomless list of options. These fall into two camps:
- Professional mastering engineers who accept submissions and payment through their online channel.
- Automated algorithmic mastering
We’ve looked into two of the most popular online mastering services for our own work: LANDR and Cloudbounce. We’re using Landr for the Mango project currently.
I ran April’s Rock Sandwich through both services to see how they compared with the “light touch” mastering I started this post with. Both services produced a master that were comparable in volume to the “Loud” version I generated. The kick drum and bass were more pronounced in both the LANDR and Cloudbounce versions, but the LANDR version sounded smoother overall, with a more even frequency distribution. The Cloudbounce version was skewed towards the treble end of the EQ spectrum which made the track sound harsh. Naturally, both services allow a certain amount of tweaking of the algorithms used in mastering. Based on the comparison, some dynamic EQ to add punch to the bass elements in the track would improve our Ozone-mastered version, but I think I would still choose the hand-mastered version, even with our beginner’s touch.
Here are a couple of articles I found while researching this post that were useful.
Here are a handful of the services I found while searching for online mastering solutions.
Let us know what you think – have you mastered your own work? Used an online service? What are you finding useful?