Join Bobby Owsinski for an in-depth discussion in this video Using the Mastered for iTunes tools Test Pressing feature, part of Mastering for iTunes.
One unique aspect of Master for iTunes is something that's not been publicized called the Test Pressing. To all artists, labels, and mastering engineers in the Master for iTunes program, iTunes will send the AAC file back via a time link to check before it's posted. The mastering engineer's then able to either audition the file with the quick listen or do a Null test in a digital audio workstation. In order to do the Null test, the Test Pressing is dropped into the Audio to WAVE Droplet and both the original source file and the new WAVE file are imported into the DAW.
One of the WAVE files is inverted out of phase by using an Invert tool. When both files are played at the same time, they should cancel each other out and result in no audio output. Any audio output after a Null test means that a different master might have been sent to iTunes to encode. Once the Test Pressing is signed off on, the song then goes on sale in the iTunes store. This has been found to be a great tool not so much for catching bad encodes but for finding more egregious errors like the wrong Master or even entirely wrong songs being submitted.
Hopefully the Test Pressing feature will be used more and more in the future. Master for iTunes is a great reason to record a mix at high-resolution, and Apple has provided the tools to help you make sure that your song sound better than ever when they're posted to the iTunes store. Best of all, your fans will love what they hear.