In some regards, iOS-based musicians are spoilt for choice; plenty of synth apps, guitar amp modelling apps, drum apps, music utility apps (like Audiobus or MIDI Bridge) and DAW-type apps but, as I’ve commented elsewhere, there are still some gaps to be filled. Perhaps the gap that surprises me most is audio editing. Yes, there are a couple of iOS audio editors in the App Store but, as yet, none of them have really grabbed ‘killer’ status.
For most musician’s, an audio editing environment would be their first choice for any DIY audio mastering work, that final stage where you add a little fairy dust to your final stereo mix such as tweaking the EQ, stereo imaging and some maximising. While this can be done within a decent DAW app (Auria has tools available for this type of work), the absence of a really top-notch audio editing environment means that mastering is not as well served as it might be within iOS.
Of course, in the wonderful world of iOS, we also get those ‘one task’ apps that provide a focused and streamlined take on a very specific task. Now, thanks to developer Igor Vasilliev, we have a dedicated mastering solution; Audio Mastering for iPad. And while the app isn’t designed as a full-on audio editor, for the specific task of DIY mastering, the feature list looks pretty impressive.
Hit the highlights
As explained by Bob Katz (one of the most respected mastering engineers in the world) in his excellent book on the subject, mastering is both an art and a science. It can also involve a whole range of different audio processing options. It would perhaps be unfair to expect a £6.99 (or $/€ equivalent) app to cover all the possibilities but Audio Mastering manages to pack in a decent suite of tools given the iOS format and the price.
These tools can best be split into two types; those that allow you to change the audio format and those that change the sound. In the former, you can convert between WAV, AIF and MP3 and change bit depth or sample rate (with dithering included to improve noise performance). In the latter, there are four components; a 10 band graphic EQ, three-band stereo width processing, harmonic saturation for adding a little warmth or sparkle and a loudness maximiser.
The other main features include a preset system for instant recall of a processing configuration and detailed virtual LED level meters that can be switched between showing input levels or output levels of your audio. While the app is not going to compete in terms of absolute feature set with something like iZotope’s excellent Ozone software (the DIY mastering choice on many user’s desktop systems), equally, it doesn’t comes with Ozone’s more substantial price tag.
Audio Mastering’s features are spread across four screens accessed via the main tabs that appear at the top of the display. No surprise therefore that the Files tab provides you with access to a list of audio files that you might wish to work with. Files can be placed on this list via AudioCopy/Paste from another app or via iTunes file sharing. I had no problem with either route in testing the app out. It’s also from this screen that you can convert the format of an audio file via the Convert Format button that brings up a set of options so you can specify what is required.
The Waveform window gives you a fairly standard waveform view of your audio and you can set things like fade in/out or loop a particular region. Do note, however, that this is pretty much it in terms of ‘editing’; Audio Mastering is designed as a processing tool and not an audio editor. The Settings page provides access to a series of global settings for the app such as ‘play in background’, the default bit depth and MP3 bit rates. In most cases, these are going to be of the ‘set and forget’ variety.
Which brings us to the Controls page – shown in the first screen shot included above – that is, of course, where most of the really interesting stuff is. Controls for the four processing elements – EQ, harmonic saturator, stereo imaging and loudness maximiser – run left to right and dominate the central portion of the window. These are based around a series of nicely sized virtual faders and are very easy to use (well, physically easy to manipulate; getting the right settings to process your audio is, of course, another matter).
Immediately above the main controls are a series of present buttons. The app is supplied with a set of seven genre-specific (rock, pop/dance, vocal, etc.) presets but you can also create your own to either replace one of these (and you can rename these via the Files window) or switching to bank B (using the A and B buttons located top-right) where there are a further seven presets slots that are initially empty. Usefully, once you have a preset selected, if you tap it a second time this instantly switches all the fader settings to a ‘zero’ position, effectively bypassing the processing options, so it is easy to do an on/off check to keep your ears from getting sucked into a ‘more is better’ mentality. Equally, the four buttons located beneath the main faders (underneath the EQ section) allow you to toggle on/off each of the individual processing sections.
In use, the four processing sections are very functional. No, they perhaps don’t offer all the bells and whistles of something like Ozone but, in terms of doing the obvious sound-shaping tasks that will appeal to wannabe DIY mastering engineers, they have plenty to offer. The EQ section does exactly what you would expect and gives enough control but in a simple-to-use format. The harmonic saturator is relatively subtle (that’s a good thing by the way) but, as you switch in the additional harmonics, gradually adds a hint of sparkle at the top end.
The stereo imaging provides faders for three bands controlling the low, mid and high frequencies respectively and there is also a master control that sets the overall level of the processing. In practice, all stereo imaging requires a little bit of care and, as a general rule, it’s best to not apply too much width expansion to the lower frequencies (or even to apply a little negative expansion) but you can get away with more at progressively higher frequencies without the mix losing it’s coherence or sounding c**p when played back via a mono system.
Perhaps the function that most people associate with mastering is making your mix louder. While this is a double-edged sword – louder means it completes better when slotted in beside a top-ten playlist of your favourite genre – if it is overdone, then it can totally crush the sonics, introduce some horrible distortion, render worthless the playing dynamics of the track and make it very tiring to listen to. That said, processing options for loudness maximisation have become much more sophisticated over the last few years so that it is possible to get louder results without doing quite so much damage.
Audio Mastering’s loudness maximiser is not the most aggressive processor of its type that I’ve ever heard (again, a good thing) but it’s perfectly capable of getting some serious additional volume into your overall mix if that’s what you require. Aside from setting the level ceiling and the speed of the compression applied, this is a one-fader task. Again, for the novice DIY mastering engineer, this is perhaps not such a bad thing as it make it difficult to get yourself into to much trouble :-)
Are you listening?
Having made your adjustments, you can then render out a new version of your file by pressing the Process button (located within the transport controls at the base of the screen) and this will automatically be given a new file name and appear within your file list. You can then compare the waveform of your new version with that of the original to get some visual feedback on what the processing has done to your file.
However, much as looking at the waveform is useful, what you really need to be able to do is trust your ears. And, of course, the only way you can do this is if you can trust your monitoring environment. In this regard, DIY mastering on an iPad is no different from mastering on a desktop audio system or in a custom configured hardware environment; to get the best from the processing tools, you need a monitoring environment that allows you to make accurate and trustworthy decisions about what sounds ‘good’ (just the same as with mixing then!).
I guess what I’m saying here is that, whatever the capabilities of Audio Mastering itself, don’t expect to get your processing choices right if you are basing your decisions on a pair of dodgy ear-bud headphones. Have a crack by all means, but you probably need to have your iPad hooked up to a good quality audio interface/studio monitors combination – or at least to have the option of taking your iPad mastered files to such a system for checking – so that you can be sure that you have improved on your original mix rather than taken things backwards.
If you want to see and hear the Audio Mastering app in action, then watch the short video….
All that said, I was suitably impressed with what I could achieve with Audio Mastering with a minimum of fuss. In the absence of access to a more sophisticated (and expensive and complex) solution, I think most iOS musicians would find this a very useful tool for quickly enhancing the mixes coming out of their DAW of choice. The EQ is effective, the harmonic saturator is subtle but useful, the stereo imaging options don’t allow you to go too far and the loudness maximiser does exactly what it says it will.
In short, Audio Mastering is a simple-to-use but highly effective tool. As the first stand-alone iOS app for DIY mastering, this is pretty impressive stuff. If your recording system is based around an iPad, Audio Mastering is most certainly worth adding to your app collection. It is an excellent example of the ‘one app, one task’ model that makes iOS so appealing as an environment to work within, but it also has enough features to make it genuinely useful.
Providing you take heed of the comments above about the need for a decent monitoring system (and which apply to any DIY mastering work), Igor Vasillev’s Audio Mastering comes highly recommended.
for readers in North America for readers in Europe
If you want to get a definitive introduction to the mastering process, then you really should read Bob Katz’s excellent ‘Mastering Audio’ book. Informative and entertaining in equal measure and well worth the investment if you are planning to undertake DIY mastering.