SACD promised even more perfect sound forever. It was hoped that it would replace CD and revitalize the music market. Alas it did not, but the DSD format is still around. Here are my thoughts on the subject.
WAV or AIFF files may appear to have tags when they are accessed through applications such as iTunes and Winamp, but in fact the data may only reside in these apps' database, because they don't actually write tags to these files themselves.