This has been happening on my PE/Win 10 realm as well. We've built an elevated dual railway and a 16x16 section of it regularly reverts taking with it the power rails.
If I log straight into a realm on the Windows 10 edition I do get music and the odd sound but most do not trigger.
I did find a workaround though. Simply open a local world and hit a block, then quit and load the Realm again and audio works as expected.
Just a note that this appears to have been resolved with 0.15.1
At least I haven't been able to reproduce it lately.