Weird thing I noticed whilst strumming along to some Mumford and Sons tracks the other day. The versions of Broken Crown and Hopeless Wanderer on Youtube (not live versions or anything, just straight studio versions) are both a semitone lower than the versions on Spotify (and the chords given online). The youtube recordings are also a little longer suggesting they have just been stretched to shift the pitch rather than being different recordings.
But why would anyone do this? I though maybe to hide from copyright police, but they are official versions and are tagged with the song details. It's puzzling me... any ideas?