I think we've found a 'fix' of sorts. So far it seems that using the 'generic' playback, rather than the 'OpenAL' playback, things are a lot smoother. I haven't experienced anywhere near as many stutters so far and no freezes or lock ups. This confirms to me that something isn't quite right with the OpenAL playback in LotRO at the moment, particularly when it comes to the ABC music system. Hopefully there can be a proper fix for this bug soon. But for now I'm going to use the generic playback as that seems to be a lot more stable.