I encountered the Sony MMCD when I fell down a rabbit hole *checks literal notes* around five years ago while researching Microsoft Encarta MindMaze[0] and its related file formats.

It turns out the data associated with MindMaze (& other encyclopedia data) changed storage format over subsequent releases of Encarta and these changes provide some interesting historical insights--including that if MS had had its way we'd all be writing web pages in RTF rather than HTML[1]. :D

You may ask, "What connection does this have to the Sony MMCD?".

Well, one of the storage formats used with early Encarta data is `.mvb` which is a format used by Microsoft Multimedia Viewer[2] (also known by multiple other names--none of which are any easier to web search :D ).

And, it turns out, "Multimedia Viewer could compile titles for Tandy Video Information System and other Modular Windows systems, as well as Sony Multimedia CD-ROM Player, a portable MS-DOS-based CD-ROM XA reader released in 1992."[2][3]

According to my research the tool "...includes software tools that simulate the look and feel of the Sony player titles on a PC" which is interesting in the context of the emulator for the Discman mentioned in the original post.

Anyway, that's the very short version of the rabbit hole--maybe in another five years I'll get around to writing up the rest...

Oh, just found my original tweet thread (including screenshots) about this rabbit hole as it happened[4]: https://xcancel.com/RancidBacon/status/1401009436949237763

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[0] https://en.wikipedia.org/wiki/Encarta_MindMaze (New as of October 2025.)

[1] https://en.wikipedia.org/wiki/Blackbird_(online_platform)

[2] https://en.wikipedia.org/wiki/Microsoft_Multimedia_Viewer (First added some time after my ~2021 research.)

[3] The Tandy VIS being a "Modular Windows" system is also of historical interest and FWIW has some support in MAME.

[4] Including screenshots of "Modular Windows Shell" and various "Multimedia Viewer" versions running under WINE.