Hello here! I own a SFS-T1 sound box, here is the setup manual for SFS-T1 and SFS-T2 parts. I don't have a lot information about this stuff and SFS-T2 is missing for working. It seems to be a very early sound developpement system for Super Famicom since 89' year is indicated on it and working with NEWS computer. All information about this stuff is very welcome ;-)
It looks like it would be pretty easy to interface to - it's just got 4 8 bit I/O ports on the connector (presumably corresponding to $2140-$2143 in the SNES memory map).
Yes I will share the photo to inside, it will be more interesting! You're right, the interface seem to be very simple.