A friend at a classical music label sent me an email this morning, saying that he was listening to an Apple Music Radio station based on a classical artist, and that he was hearing some distortion in the music. When he listened to the same track on Apple Music, there was no distortion.
“Aha,” I said, “Have you not read this article on my website?”
It’s worth mentioning again: iTunes Radio (now Apple Music Radio) Normalizes Playback Volume with Sound Check. It uses Apple’s Sound Check feature, which is designed to make sure there’s not too much difference between the volumes of tracks on radio stations. This prevents jarring changes in volume, but it ignores the often large dynamic range (the difference between the softest and loudest parts) of classical music.
Here’s one example, from the older article, of Miley Cyrus’ Wrecking Ball. The first part of the waveform below is from the iTunes Store version of the track, and the second from the iTunes Radio version:
The quiet part of the song is much louder to match the overall loudness of the track, but also to be in line with the desired volume of the Apple Music Radio stations.
So be aware that when listening to Apple Music Radio, you’re not hearing the music unaltered; it can be louder or softer, and, for quiet music, there’s a good chance you’ll hear distortion.