Apple Digital Masters
By starting with the best possible masters we are able to offer our Apple Music and iTunes customers the highest possible quality audio. Our latest encoder can take advantage of every bit of the high-resolution masters that engineers are creating especially for us. The results, both for streaming and download, are virtually indistinguishable from the original 24 bit studio masters.
Here is some history and information that guided those decisions as well as instructions for the use of the Apple mastering tools.
Read this : Apple Digital Masters
To hear how music will sound after it’s encoded and to help make important creative choices during the mastering process, download these tools. The Apple Digital Masters droplets are simple, standalone drag-and-drop tools that automates the creation and decoding of 256 kbps AAC encodes using the Apple AAC encoder. AURoundTrip and afclip are now included in the latest versions of macOS. For earlier versions of the OS use the links below.