Quick question, as asked in the title. The reason for asking is that I was browsing Amazons' site and noticed a number of Blu Ray music discs but some are re-mastered from concerts recorded before Blu Ray was "born". Just wondered how much of an improvement the audio would be over the DVD version mastered from the same source. So, do all discs have HD audio. As an aside, are we likely to see (or rather hear) any Blu Ray Audio discs, like DVD-As?