As for MiniDisc being "dead", on behalf of myself, GuitarFxr, bobt and many others from the old MDCF who still use it, all I can do is say this.....
BULL.
As for Sony and ATRAC, Sony mis-marketed (at first) the MD as the successor to CD, in which it is not. But, it is the perfect replacement for the ever-flawed cassette tape, and when I got into MD back in 1998, I pretty much did away with using cassette tape as a recording medium.
How ever you are right that the market wanted to carry more than just a few MD's worth of music, that is why, even with Sony trying to counter with Hi-MD, that the format failed, but, only on the portable playback unit basis. Even I gave in by getting a few NW-HD5 units, many for parts or accessories that came with them, and 2 others that were N.O.S. (new in U.S. blister package!!!) at that!!!
I still use MD on a regular basis for all home, car, and studio recording purposes, including for upload (through my MZ-RH1, in which I own 3 of) onto SonicStage CP 4.2 to my NW-HD5 HDD Walkman, so the ATRAC family of formats is still alive and well here at BIGHMW.com Headquarters. I also use it to record most of my vinyl and cassette collection to preserve the original tapes (many of them over 20 years old from my days in high school and having gone to school with Cindy Margolis for a year at that in 1983-84!!!), and we all know what happens when you run a tape over and over... it wrecks it that much more, so MD can still be quite handy when needed.
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