Mastered For iTunes

From Apple Inc., "Mastered for iTunes" is their PDF guide for those interested in selling their music on iTunes.
We’re committed to delivering music exactly as the artists and sound engineers intend it to be heard. Housed here are the information and tools necessary to create the highest-quality masters for iTunes. Learn more by reading the Mastered for iTunes technology brief.
This is certainly worth a read and not nearly as evil as one might have thought. You can go to the Apple webpage or download the "Mastered for iTunes" PDF.

Here's my favorite part (with emphasis added):

To take best advantage of our latest encoders send us the highest resolution master file possible, appropriate to the medium and the project.

An ideal master will have 24-bit 96kHz resolution. These files contain more detail from which our encoders can create more accurate encodes. However, any resolution above 16-bit 44.1kHz, including sample rates of 48kHz, 88.2kHz, 96kHz, and 192kHz, will benefit from our encoding process.

Don’t upsample files to a higher resolution than their original format. Upsampling won’t recover or add information to an audio file. Don’t provide files that have been downsampled and dithered for a CD. This degrades the file’s audio quality.

As technology advances and bandwidth, storage, battery life, and processor power increase, keeping the highest quality masters available in our systems allows for full advantage of future improvements to your music. Also, though it may not be apparent because there may not always be a physical, tangible master created in LP or CD format, the iTunes catalog forms an important part of the world’s historical and cultural record. These masters matter—especially given the move into the cloud on post-PC devices.

Some day (maybe soon?) Apple Inc. will flip that big 24/96 switch and let the HD love flow.

mcondo's picture

Is this a new document/process, etc? If it is then 24/96 would seem to be right around the corner. 

Michael Lavorgna's picture

Is the date on the PDF doc. I did not see previous revisions (I'm assuming these guidelines have existed for some time) but I'll keep my fingers crossed for "right around the corner".

Michael Lavorgna's picture

 ...and it's worth a read:

Mastered for iTunes: how audio engineers tweak music for the iPod age

And don't miss the comments where people dictate what's good enough for them and us when it comes to the quality of the experience of listening to music on the hi-fi.

You know it's really the same as cars, wine, food, cameras, etc. where there really only needs to be one generic choice since no one needs that expensive stuff.

gallardo's picture



24/96 ??? 

I hope The good Lord help us to get that on iTunes !!!

mcondo's picture

I found this link about 24/96 over on the Apple support boards. It has over 15,000 views! I can't believe Apple woud just ignore that kind of interest - although I understand that they will get around to it when it makes sense to them.

Vincent Kars's picture

The way I read the PDF:

Apple goes for 24 bit / 44.1 kHz regardless of the sample rate of the master.

No 96 kHz I’m afraid


Apple’s latest encoding methodology is a two-step process. The first step in the encoding path is to use state-of-the-art, mastering-quality Sample Rate Conversion (SRC) to resample the master file to a sample rate of 44.1kHz.

Because this SRC outputs a 32-bit floating-point file, it can preserve values that might otherwise fall outside of the permitted frequency range. This critical intermediary step prevents any aliasing or clipping that could otherwise occur in SRC. It is this 32-bit floating file that’s used as the input to the encoder and is one key reason for such stunning results.

Our encoders then use every bit of resolution available, preserving all the dynamic range of a 24-bit source file and eliminating the need for dithering. The advantage of this is twofold. Not only does it obviate the need of adding dither noise, it also lets the encoders work more efficiently as they don’t need to waste resources encoding this unwanted and unnecessary noise.


Or if starting with WAV LPCM file at 48kHz or 96kHz sample rate:

1. To downsample to 44.1kHz LPCM using optimal sample rate conversion and add Sound Check information, in Terminal, type on one line:

afconvert source.wav -d LEF32@44100 -f caff -- soundcheck-generate --src-complexity bats -r 127 intermediate.caf


Michael Lavorgna's picture

The point I'm making is very simple and straightforward - Apple is asking for 24/96 "masters". And they also say this:

As technology advances and bandwidth, storage, battery life, and processor power increase, keeping the highest quality masters available in our systems allows for full advantage of future improvements to your music.

Which leads me to conclude that they may very well offer 24/96 at some point.

Vincent Kars's picture

At least we can expect some Redbook without dither in the near future.

deckeda's picture

... that an optimized-for-AAC 24/96 master be sent to Apple, which is what Apple is asking for. If and when Apple sells 16/44 or 24/94 lossless files from those sources, I don't see how they could sound right.

They're telling us right now, upfront, that these have been altered and EQ'd to overcome deficiencies inherient to AAC (or earbuds, or whatever, depending on one's interpretation of Apple's claim that Mastered for iTunes will work well on any playback situation.)

Michael Lavorgna's picture

They are telling us that the remastered for iTunes version should take into account the intended audience.

Because iTunes Plus is a highly portable format, its files have the potential to be listened to in a wide range of different settings. So while one listener may be using white earbuds while riding in a loud subway car, another may wind up listening intently to a Bach cantata on AirPlay‑equipped Bowers and Wilkins speakers or on a similarly equipped Denon receiver in a home media room. Just as likely, a college student may be deep into Miles Davis' Sketches of Spain while sporting Dre Beats headphones in the campus library. Keep in mind that Apple has sold more than 250 million iOS devices, and that many, many people around the world are listening to music on their iPods, iPhones, or iPads.

You’re being provided with all the tools you’ll need to encode your masters precisely the same way the iTunes Store does so that you can audition exactly what they’ll sound like as iTunes Plus AAC files.

Further, to ensure that your audience is hearing your intended sound, Apple recommends listening to your masters on the devices your audience will be using.

So yea, I'd imagine some music may sound like crap and some may not. But I don’t see how this differs from any other format.

But if you are suggesting that if/when Apple releases their 16/44 or 24/96 versions for sale on iTunes that they are all necessarily going to sound like crap, and that Apple is either unaware of this issue or they simply do not care, then Apple sure has a large problem on their hands and I won’t be buying any of their crappy sounding music.

How likely this scenario is depends on one’s attitude toward Apple and has little to do with the contents of this document, imo.

deckeda's picture

that I'm engaging in, although not without some justifiable reason to worry. It (i.e. any eventual hires offerings from Apple) could turn out to be a similar situation for audiophiles that exists with other formats, where SACD reissues are compared to DVD-As are compared to are compared to vinyl old and reissued: each flavor could be different (Ella and Louis notwithstanding ...)

Again, somewhat ironically(?) this is where vinyl's technical limitations could have the advantage: where mastering for an intended digital format seems to be quasi-optional (it apparently has been up until now for the iTunes Store) it can't be for vinyl.

The fly in the ointment for vinyl is the same as it is for anything else, regarding the Loudness Wars. If the producer made the mixing engineer leave a squashed mastering chain tacked on, the vinyl's mastering engineer wouldn't have much to work with, and the LP would be just as dynamically compressed as many modern digital songs are.

A separate but inescapable concern when discussing "formats" for consumer purchase, which is why you got the responses you did above.

Michael Lavorgna's picture

Sorry, couldn't resist.

Greg Heimbecker's picture

One of the best things at the 2011 RMAF was the seminar on " The Future of High-Resolution Computer-Based Audio " hosted by David Robinson of Positive Feedback and featuring Cookie Marenco; Andreas Koch; Bruce Brown, Puget Sound Studios; David Chesky, Chesky Records /; Jonathan Tinn; Danny Kaey, Apple. There was an incredible wealth of info on hi res downloads and particularly on DSD downloads. Compared to the depth of info coming from Andreas Koch, Jonathan Tinn and Bruce Brown the persistent interjections from Apple's Danny Kaey seemed like a NAMM show barker. Hardly appropriate for a room full of highend devotees... iTunes is convenient, we get it... I finally took it upon myself to ask him when Apple would at the very least give us lossless downloads let alone anything genuinely high def. He responded that hardly anyone heard the AACs available in their full glory and that we should concentrate on better decoding. I responded that in this room he was preaching to the choir and that both ends of the equation, playback systems and CONTENT needed to be addressed concurrently. Unfortunately Apple tends to think in billions of units and the meer thousands of us interested in quality playback represent but a niche market at best.

It is reassuring to see that they understand that keeping quality as high as possible to the last possible moment in the production chain makes for better final product. As a recording engineer I take some modest solace in that...

Michael Lavorgna's picture

I also think we can see who is the dominant partner in the marriage of technology and music at Apple.

Maybe we should look at this situation as being similar to the early days of the phonograph where Edison wasn't even thinking about music.

Sound_Doc's picture

I'm sorry, 24-bit depth is great, but what happened to 192?, If you want to sample fast enough to really catch percussive materials, and that includes rim shots and gun shots, you need to sample faster than 92. So, I don't think of 92 as HD.  SACD is effectively faster than 92 and if you have a recording in both formats and a reasonable set of speakers or earphones as well as reasonable hearing, you can tell the difference with SACD sounding more HD than 92. So, yes, by all means keep the source material as HD as possible and then give it to iTunes to degrade. And, I do agree, almost regardless of the software paradigm used, upsampling really doesn't improve the recording, it just makes guesses about what would have been there if the recording haed been done in a higher format in the first place.  I have hear some upsampled stuff that is atrociously worse than the original source.   

Michael Lavorgna's picture

Ideally 24/192 would be great but we're talking about Apple's existing policy. Besides, I've heard perfectly lovely music from 16/44 rips and would suggest the quality of the original recording has more to do with the end result than bit depth and sample rate.

Of even greater importance is how we feel about the music.

Rich Davis's picture

higher res files take up more room on mobile devices, their servers and obviously will take longer to download.

A way around it?  

Just get a Meridian Director USB DAC and use that instead.

A lot of these record labels will get around to creating higher res files when they get around to it.  It's like getting SACD, only a small handful of content was done on SACD or DVD-A.

So, we can either get whatever content we can get through whomever or just use a Meridian DAC.


No, I don't work for Meridian or a Meridian dealer.  I just like their products a lot. :-)