Hi,
I'd agree with everything JC noted about HDCD, and only add one thing. If memory serves, HDCD is essentially a dynamic-range expansion system, adding as much as 12 dB to the dynamic potential of a recording. In tests I did years ago, you could detect the difference (barely). The HDCD decoding was licensed out to some manufacturers but I don't think it was all that successful, mainly because the difference between an HDCD recording and non-HDCD playback was so difficult to hear. Frankly, the conventional CD format is able to encompass the entire dynamics of any orchestral/musical performance so I didn't really see the point of HDCD.
As JC pointed out, Keith Johnson is an excellent recording engineer and I've used several of his recordings as definitive test discs for listening tests, HDCD or not.
Alan
