What does it mean to “master for iTunes?” Apple tripped that question with the launch of a suite of utilities and sound-processing algorithms intended to master music for their codecs and software, rather than more generically as would be done with the CD. More significantly, what does it mean that an increasing number of music listeners experience all music through Apple’s software as the final gateway to their ears? In our first look at this issue, we welcome guest writer and producer Primus Luta (David Dodson). He tests this issue the only way that really matters: with his ears.

There’s so much to say, in fact, that almost each line here of David’s conclusions is up for potential discussion and debate. That to me isn’t a red flag for posting – quite the opposite, it’s an invitation. So we consider this the beginning, not the end, of this conversation. -PK

The announcement of Apple’s new Mastered for iTunes suite caught me at a serendipitous time, as I prepped the first release on my new label.  In fact, the day of the announcement came right in the midst of reviewing masters for the release.  It’s an interesting situation for a compilation release, in which styles range from ambient to muddy beats.  Finding a good balance that keeps them all flowing together is an art in and of itself.  But it would seem Apple has that all solved with their Master for iTunes droplet.  Drag the high-quality files to the droplet, and presto-chango — out come files that all play perfectly in iTunes.

Well, that’s the claim, but is it mastering or encoding?  To their credit, in the documentation Apple explains that their 32-bit process manages to encode from high-res audio without leaving a dithered footprint.  Ed.: “Dithering” is the addition of adding small amounts of noise to compensate for errors that can occur in downsampling from greater bit depth to less – it’s used in image processing as well as in sound. According to Apple, their use of greater bit depth in the intermediary file prevents aliasing and clipping, and thus they don’t need to use dithering. -PK Apple’s tools aren’t the only way to do this. Most pro audio editors can achieve the same, but often people are ripping MP3s or AACs in their media players, so it is an important distinction.  It still begs the question: why go down to CD specifications,  especially while making the point of noting their process results in a quality better than CD’s or CD rips? Ed.: The greater bit-depth is only an intermediary file; eventually delivery is not only compressed, but at specifications set by the CD. Greater resolution and bit depth are limited to the mastered files, not to what the listener ultimately hears.

The most important question, though, is how does it sound?  If you send a song to be mastered, you expect in general to get back a song that sounds different than the one with which you started.  Generally, this difference is in perceived overall volume, but also can include changes to dynamics and other touches.  So what changes does the Master for iTunes droplet make to your files?  Well, none: it just encodes them.  They describe the process as such:

The Droplet creates an AAC audio file from an AIFF or WAVE source file by first generating a CAF (Core Audio File) rendered with an iTunes sound check profile applied to the file. If the sample rate of the source file is greater than 44.1 kHz, it’s downsampled to 44.1 kHz using our mastering-quality SRC. Next, it uses this newly-rendered CAF to render a high-quality AAC audio file. Once the final AAC audio file is generated, the intermediary CAF is deleted.

The key part relating to how your files sound is the “iTunes sound check profile applied to the file.”  Rather than changing the volume gain in the file, metadata information is used to tell the playback device how to play it.  What the documentation does not tell you is what or how this information is determined.

Reviewing masters involves listening on many different systems.  I like to listen on studio monitors, a small boombox, a consumer surround sound theatre system, laptop speakers, desktop computer with headphones and, of course, in a portable media player with various headphones.  I’ve also added a cloud-based stream to that mix — and doing that is what brought me to the experiment I conducted.

I uploaded a test master to the the cloud and was comparing listening to it and iTunes, when I noticed a rather huge discrepancy in volume.  At first, I figured they were just set to different levels, but upon checking both were at their max.  So I went to play my reference song, which currently is the title track from Monolake’s new album Ghosts (I tend to try to keep my reference material relatively contemporary.)  The volumes on this track between applications were more or less the same.  Meanwhile, my test master, which was playing pretty much on par with the Monolake track from the cloud, played significantly lower in iTunes.

That was when I remembered Sound Check.  I wasn’t on my normal listening computer and never bothered to see if Sound Check had been enabled, but sure enough, when I looked the preference was checked.

Ed.: I actually had some difficulty getting a solid answer, but consulting with Apple-following journalist Jim Dalrymple of The Loop, we believe that the default setting is off in iTunes for Mac and Windows and on iOS. If someone has a different answer to this, I’d love to hear it. What you can tell about it is what Apple has documented in support document HT2425, namely, Sound Check operates track-by-track, not album-by-album, operates in the background, and computes and stores non-destructive normalization information in ID3 tags. It works exclusively with .mp3, .AAC, .wav, and .aiff file types, and gain increases occur before the built-in iTunes Limiter. That also means you should consider the iTunes Limited as part of this process.

As soon as I disabled it, the volume was consistent across players.  This inspired me to test how Sound Check was affecting other files, and so, going through my iTunes library, I built up a sample set of 25 songs to test the effects of Sound Check:

- = Sound Check turned down the volume
+ = Sound Check turned up the volume
null = Sound Check had no effect on volume

This was all done by ear, and while my ears aren’t what they used to be, I’m willing to guess if you tested, your results would be similar.  Ed.: You should also be able to investigate the actual ID3 data, but in this case, perceived volume may be more interesting anyway, and the effect isn’t necessarily subtle.

About halfway through, I thought it’d be good to confirm these findings with numerical tests, but then I started noticing a pattern.  Almost everything gets turned down, some more extremely than others — the most extreme example being the Nine Inch Nails track.  The two tracks that get turned up are both archival recordings, and so it makes sense that they are at a lower volume.  The vinyl rip from Pharoah Sanders would likely have gotten turned down, as well, save for the fact that vinyl rips are re-mastered to raise their volumes.  Same goes for the live Stevie Wonder boot.

The stand-outs are the ones which Sound Check has no affect on, each of which was released within the last two years. The Tori Amos track comes from her last orchestral album.  Because of the result, I tested two other selections by her on either side of the advances of digital technology, both of which get turned down.  The track “Blood Roses,” like “Night of the Hunters,” features no drums but still gets turned down, as the mixing for the album is definitely rock-influenced and so the harpsichord falls on the loud side.

Stellar OM Source’s track is of the ambient drone variety, also without drums.  But the Monolake track is techno, full of drums and crunching distortions, yet it remained unaffected by Sound Check. (It’s also worth noting that the Powell track, which also has prominent drums, is only barely turned down by Sound Check.)  Because “Ghosts” is one of my reference tracks, I had previously done an analysis of it. I noted that, despite peaking at the max of 0 dB, its RMS only averages out at -14.5 dB.  I’ve done this type of analysis for a number of modern tracks and this is unusually low.  Typically, drum- and bass- heavy tracks manage to hit around -10 dB RMS with some going as high as -6 dB RMS.

The results for the Monolake track led me to hypothesize that what Sound Check was actually doing was applying an RMS limit on tracks of around -15 dB (with a +/- that I haven’t calculated yet).  Anything below that gets turned up and anything above that gets turned down (with the precaution that turning up never results in clipping by going above the 0 dB max).  This was confirmed when I normalized one of my test master’s to an RMS of -15 dB.  This version of the track, when played in iTunes with Sound Check enabled, played at the same volume as with Sound Check disabled.

Where an object of mastering is to create a version of a song which plays at the optimum level across playback devices, where iTunes is understood as rapidly becoming a primary application for playback, and where Sound Check is often enabled as a preference in iTunes, it stands to reason that those producing masters today should be working to create versions of songs for which Sound Check does not need change the levels.  As such, mastering for iTunes can be understood as creating a quality master which has an average RMS of -15 dB.

Prior to this, the primary barrier for the levels of a master was the 0 dB max limit to prevent clipping.  Within that, the RMS levels could fall anywhere, which is the freedom that gave way to the loudness wars. The so-called “loudness wars” refer to the increase in compression to produce greater perceived loudness, as tracked over the rise of big FM radio and the CD through the 80s, 90s, and today.  Two songs with a max of 0 dB can have extreme differences in volume based on the RMS.  Production and mixing tricks, especially with the heavy use of dynamics processors like compressors, can squash a song, allowing the overall volume to be raised incredibly.  Using these techniques, it’s entirely possible to create a mix (not a master) which has a max level of -4 dB but an RMS of -10 dB.  If you master that track, raising the max, to 0 dB, the RMS level will push close to -6 dB.  When this file is played in iTunes with Sound Check enabled, however, it’s going to be turned down to -15 dB RMS which will be below the -4 dB max level that it started with.

The potential of adopting this as a standard is an end to the loudness wars as we’ve known them.  As the above example shows, doing everything you can to push a song to the max ends up having the opposite effect.  So rather than worry about loudness, producers and mixing engineers can return to focusing on getting good, clean mixes of songs.  Mastering engineers can also worry less about pushing the volume to the max and focus on bringing the best out of the mixes.

Incidentally, the system for producing tracks that comply to this have long existed in the mastering world, thanks to Bob Katz and the K system of level metering.  Using the K-14 system of metering for mastering (and producing and mixing) can ensure that engineers are not pushing their mixes too loud.

There are, however, some negatives which can be attributed to the adoption of such a standard.  Because of the headroom afforded by digital, in the last decade, the creative use of volume has increased.  ”Loud” has new musical meaning, and the tools utilized to maximize loudness normally in mastering are being introduced during production to create effects.  An example of this is the pumping effect of side-chain compression on drums.  This can be quite appealing creatively even when (and perhaps because) it pushes to levels of distortion.  Creating this effect without clipping is easily managed with a limiter at the end of the signal chain.  However, creating this effect below -15 dB is not so straightforward, and the results won’t necessarily be the same.

For the mastering of multi-song projects there are other issues.  Over the course of an album, dynamic shifts between songs can help to carry the mood of the project.  One wouldn’t necessarily want all of the tracks to have the same -15 dB RMS; ideally, that would be reserved for the loudest song and the others mixed under that accordingly.   It presents a challenge, but it is manageable.  What’s nice about this type of limit is that, unlike the 0 dB max limitation, going over it does not necessarily result in destructive clipping, so there’s still a dynamic range within which to work.  It’s also worth noting that the Sound Check process can be applied to an album to ensure consistency in listening.

One has to hope that, should this become a standard, new creative ways of working within these parameters will be born.  To be clear, -15 dB RMS, while not the loudest, can sound great for a great mix.  Just listen to the Monolake track if you want proof.  Getting people to adopt to it is a challenge, but I think the incentive to adopt will be there once artists realize that the more they push the volume, like their mother, the more Sound Check will turn the volume down.

As a footnote, I thought to test how Sound Check treated what was previously considered the most perfect album from a mixing mastering perspective – Steely Dan’s Aja.  In iTunes, Sound Check turns “Peg” down.  So it’s not just your bass heavy-beats that could be affected by this.  Also, it’s not just iTunes and not just Sound Check.  Replay Gain is a similar tool found in other media players.  Spotify also has similar limiting for its streaming services.  These things will likely show up in more playback applications as time goes on so adopting to this now is a pretty safe bet.  Sure, your tracks may not sound the loudest when tested without these services, but with good mixes, they will still sound good, regardless. “Good” is far more important than “loud.”

I’m still on the fence, though.  In general, I’m not a fan of auto volume control.  Adopting a mastering standard that caters to them just seems wrong, even if I am (for the most part) on the side of ending the loudness wars.  And, again, on the creative side, I’m very concerned.  A decade of loudness wars in many ways has changed our sense of sound possibilities, and signals pushed into the red — well, I kind of like those, when they’re done creatively.  People talking about the loudness wars are usually talking about traditional rock and pop music being squashed and absent of dynamics.  But we’re at a point now where there are other genres for whom pushing into the red can be seen as more valuable than dynamic range.  It’s a completely different school of thought and need not be shut down (or turned down) because of an antiquated sense of norm.

You can follow David Dodson on Twitter. http://twitter.com/#!/primusluta

We’re interested to hear what you think.

You’ve heard the gripes, and heard and seen the somewhat unscientific demos. Now it’s time to examine the over-compression of music with – science! Earl Vickers of STMicroelectronics examines the Loudness Wars in an academic paper, as noted to us by reader photohounds.

The Loudness War: Background,
Speculation and Recommendations [PDF Link, sfxmachine.com]

The paper comes from last November, but it’s as relevant as ever. It’s not just the usual take, either. Its history begins with Phil Spector and vinyl, considering the impact of broadcast TV and not just the music industry. It notes the evolution of compression technologies, particularly multiband technologies.

Most importantly, though – and I’ve spoken regularly to mastering engineers about this – the paper turns to the issue of listening fatigue. Here’s one whithering criticism of the industry on that: some engineers even believe that thoughtless over-compression could be to blame for the decline of the entire industry.

Mastering engineer Bob Ludwig stated, “People talk about downloads hurting record sales. I and some other people would submit that another thing that is hurting record sales these days is the fact that they are so compressed that the ear just gets tired of it. When you’re through listening to a whole album of this highly compressed music, your ear is fatigued. You may have enjoyed the music but you don’t really feel like going back and listening to it again.”

You’ve seen much of this before, but rarely in such well-annotated, comprehensive form.

Best of all? The conclusion applies lessons from Game Theory to work on making the loudness wars come to a conclusion.

Here’s another thought, too: with artists increasingly self-releasing or releasing through more specialized labels, greater access to music online, direct-to-consumer distribution, and online replacements for conventional terrestrial radio, many of the factors that produced some of the oddest hyper-compression at the top of the charts are fading into the background.

Pax Musica for the loudness wars, anyone?

Are you sick of the death of dynamic range? Are you mad as hell at squashed audio that means to be “loud” and only wind up with the actual sounds smooshed out? Alternatively, are you guilty of some detail-squishing dynamic abuse yourself?

A campaign is on to get the dynamic war out of comment threads and forums and onto the streets. Taking a positive tack, the Pleasurize Music Foundation isn’t simply attacking overcompression and dynamic distortion: they’re suggesting an alternative path, in which restored dynamic ranges bring back joy to your life. There are opportunities to sign up as listeners, labels, producers, mixing and mastering engineers, even the consumer electronics and music tech industries.

There’s also a free (Windows-only) plug-in for checking the dynamic range of your mix. There are plenty of other tools that do the same thing, but the idea is nice.

pleasurize music!

Thanks to Mormo at Basement Hum for the additional heads-up.

Now, the idea of crushed dynamic range is nothing new. But via comments, mastering engineer Tobias Anderson points out that it’s not always the mastering that’s to blame — some people are actually distorting at the digital conversion stage. (That’s, incidentally, not the fault of digital recording, either – to screw that up, you have to be really careless, which evidently people are.)

Tobias’ comments below. Now, obviously, this is an issue that can generate some controversy. But start talking about simply preserving dynamic range? I think just about everyone can get behind that. The idea of “quality” can often be loaded, but talking about dynamics as pleasure is as universal as hearing.

As a mastering engineer, it has become increasingly disconcerting to both work on and listen back to much of todays’ music. Distorted, compressed & messy sounding to say the least! However, 2 points I must make:

Firstly, compression and brick-wall limiting are NOT the only factors involved in making a record loud and / or distorted. The clipping of the ME’s ADC (analogue-to-digital-converter) is the most aggressive form of distortion you will hear on todays’ loud records. Digital limiters are generally (hopefully) not cranked too much (between 1-3db), but rather the load should be spread across more than 1 unit, making the effect less obvious than if the same amount of gain reduction had been employed with a single unit. The signal is then fed back to the ADC, and ‘clipped’ to achieve the final loudness increase. The maximum peak level of digital audio is 0dbfs, however when clipped, the incoming audio exceeds this value (up to 6db, maybe more in ridiculous cases!) and the loudest peaks of the music are literally shaved, or ‘squared’ off. With the upper end ADC’s, this process can be fairly transparent, if used ‘sensibly’ (if that is possible..) however when abused, it sounds truly awful as you all can hear. One example (many are available that springs to mind is the Foo Fighters’ Nothing Left To Lose album. Every time the snare is hit, the digital distortion is unbearable, the high frequencies sound grainy and harsh ect ect. However, audibly, the effect of clipping differs greatly from the effect of brick wall limiting, which can, as previously mentioned, and subjectively speaking, benefit or compliment a particular style or genre of music. Dance, hip-hop & drum n bass coming to mind especially. This processing DOES impart a certain sense of power to the sound which is very different than simply using compression alone on the mix buss or on the individual elements in the mix.

Secondly, music is never ‘cut’ or HPF’d (high-pass filtered) at 80hz. 40-45hz maybe, a gradual roll-off from 80hz-20-30hz probable, but there is still a lot of important musical information below 80hz that is needed in modern music, even if it can’t be reproduced by poor consumer listening equipment. The 60hz(ish) peak in a hip-hop kick for example, would sound completely wrong and hollow if the fundamental frequency lived in the 100hz range for example. I can’t think of a commercially released modern record that has been released with very little or no musical information below 80hz, not impossible, but certainly not the norm by any stretch. Lastly, having a ‘pre -mastering’ chain is really not a good idea, and will probably do more harm than good in most situations, unless: the listening environment is very good and the engineer is very skilled. Using a particular compressor for a desired character on the mix buss prior to mastering, is a very valid ‘mix’ technique, but again the engineer must be very competent for this to be worthwhile.

I hope this has shed some additional light on the loudness war for you all.

If you would like to express your dislike for the practice, in hope of eventually stopping it, please visit and register for free at

www.dynamicrange.de

Toby Anderson

As the rest of us lament brick-wall limiting and other techniques for flattening dynamic range and making music louder (see Music Thing’s recent discussion), WWAYM is sponsoring a no-holds-barred, Monster Truck Ralley of audio engineering. The contest: make it as loud as you possibly can.

The competition, sent to us by reader Adrian Anders, “must be as loud as possible but with taste.” (Does ‘taste’ disqualify redoing all the vocals with Hatebeak the death metal parrot?) The award is a license to WWAYM’s own mastering tool, which they’ll use to recreate thing winning entries more easily. I say do it for the bragging rights instead.

Unfortunately, the stipulation that “only legal tools” may be used probably means “no pirated software.” Damn. I was hoping for some sort of street-illegal maximizer/limiter.