“Can you make them sound better?”
Making special masters for digital delivery is in fact nothing new. Long before Apple offered official guidelinesfor audio engineers to follow, mastering engineers already made their own attempts to create master recordings that sounded “better” when compressed into the standard iTunes Plus format. Even in the early days of the MP3’s rise to popularity, mastering services offered custom encoding.
“In the early digital delivery days, each mastering engineer experimented around until he found an encoder that he liked,” Hull said. “But it always depended on the source material. Different encoders worked differently on jazz as compared to dance music, for instance.”
Apple has always done its own encoding for the iTunes Store, but other stores that sell MP3s generally allow direct uploading of compressed files. Remastering source material for different encoders wasn’t practical, but choosing a specific encoder to best match the source could give better results. “So we would encode them ourselves and try and make it better, and we could in fact make them sound better,” Hull said.