Thanks for explaining how long it took to load msx games. I can only remember needing 15 minutes to load 128k spectrum games.
So glad the MSX has roms that can load instantly. 
So glad the MSX has roms that can load instantly.
As a result nobody wants the cassette tapes, so for collecting MSX software on the cheap cassette games are much more affordable if you don’t mind it . And I suspect that games which were only released on tape are probably relatively lesser known and perhaps underappreciated.
Mass storage devices access is performed through bios, and these bios routines work only when interrupt is disabled.
I don't know about the other mass storage cartridges, but at least the newest drivers for the IDE and SD-Mapper do not disable the interrupts on disk access. So it's perfectly possible to play music while loading data.
It wouldn't be exactly a very long tune though, since the loading is very fast.
Probably more useful for mid-game loading without pausing the BGM.