First and foremost: what you have is not for the SNES or SFC. The SNES/SFC has a
62-pin cartridge connector (31 pins per side), while what you show
in your photo has 64 pins (32 pins per side).
Guess what console has a 64-pin cartridge connector? The
Genesis/Megadrive. This also explains why the PCBs have "Sega" silkscreened on them. So I'm curious why you posted this in the SNESdev forum -- did someone who sold you this tell you it was for the SNES/SFC? If so they either lied or were wrong.
Next: you appear to have at least two PCB/carts (I can tell from the silkscreened model numbers as well as the blue vs. black EPROM sockets). Can you please upload some higher resolution photos? The ones you've uploaded look like they were taken from a mobile phone in what I would classify as low resolution (the pictures are 640x480). I'm left wondering if they chips are either FM synthesis chips / OPL chips, especially with your claim that it's "music dev hardware". We really need to see the silkscreening, clearly, on all the non-windowed (non-EPROM) chips to know what's what. :-)
Finally, the double-ended cable you have is a 37-pin cable. Not sure what it connects to, given that I don't see a break-out socket or dongle that attaches to any of the PCBs. Possibly it went to an input device (keyboard, sequencer, etc.) if the PCBs are in fact specific to music development, or possibly it went to a special Genesis/Megadrive unit that had such a dongle on it. I only got to see later development kits (for systems like the Saturn and the original PlayStation) when I worked at Z-Axis (gaming company) briefly.
EDIT: I renamed this thread from "SNES Development Hardware", and moved it to the "Other Retro Dev" forum given that these PCBs aren't SNES/SFC dev boards.