The AES have released a new/revised recommendation concerning loudness for internet audio streaming and on-demand application. There are no real surprises in there, with a -18 LKFS/LUFS (+/- 2 LU) integrated loudness for assorted content where the dialogue is not directly measurable on its own, which is in line with previous recommendations, as posted about previously.
For music streaming the recommendation is -16 LKFS/LUFS (+/- 0.2 LU) for track normalised content, which is a little lower than the average of -14 LKFS/LUFS that would be considered more standard currently, however this is to allow for album normalised content to have a highest level of -14 LKFS/LUFS, with the “average” song being 2 LU quieter than the loudest song.
The document has some good discussion of some of the issues at play in this area, including high dynamic range content, and some suggestions for playback device manufacturers. You can read the full document at:
https://www.aes.org/technical/documentDownloads.cfm?docID=729