The Roland D20 is a classic electronic synthesiser with a built-in floppy drive, used for saving MIDI sequences and samples.
Weirdly, it seems to use precisely the same format as the Brother word processors: a thoroughly non-IBM-compatible custom GCR system.
FluxEngine supports both reading and writing D20 disks, as well as basic support for the filesystem, allowing files to be read from and written to D20 disks. Note that the D20 was never intended to support arbitrary files on its disks and is very likely to crash if you put unexpected files on a disk. In addition, while the file format itself is currently unknown, there is a header at the top of the file containing what appears to be the name shown in the D20 file browser, so the name by which you see it is not necessarily the filename.
A word of warning --- just like the Brother word processors, the D20 floppy drive isn't very well aligned. The drive itself uses quarter-stepping to automatically adapt to whatever alignment the disk was formatted with. This means that trying to read such a disk on a PC drive, which does not have adjustable alignment, may not work very well. In these situations it is possible to adjust the alignment of most modern drives, but this is a somewhat risky process and may result in permanently wrecking the drive alignment.
Please get in touch if you know anything about it.
Many thanks to trondl on the VCF forums for assistance with this!
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To read:
fluxengine read rolandd20 -s drive:0 -o rolandd20.img
To write:
fluxengine write rolandd20 -d drive:0 -i rolandd20.img