Not at the moment, but it is not entirely impossible that it might some day. It wouldn't be an awful lot of work to make defMON work with an interface like that (if I'd only find the time). I'm not making promises though.
What you're linking to is a standard MIDI interface for the C64 and they are quite straightforward to use from a coder's point of view. There is a whole family of MIDI interfaces for the cartridge port that all more or less work the same way. You can see a list of those interfaces here, and the DATEL one is included there:
Just a few years ago there was also a MIDI cart called something like Kerberos MIDI developed, but it is now sold out. That one was also similar to the midi cartridges listed on that codebase page if I remember correctly. Not 100% sure though as I never really looked into that one.
The only "problem" is that in these days most people use something like a 1541 Ultimate cartridge or similar that occupies the cartridge port, so from that point of view using the cartridge port for MIDI connectivity isn't really desirable. This is also the main reason for making that defMON sync interface for the user port instead, since that one is not used by other hardware on most people's C64 setups.
There are also other benefits of having a cartridge like Action Replay, Final Cartridge or Retro Replay in the cartridge port (which is what you would have if you've got a 1541U2 sitting in the cartridge port). For example, defMON makes use of the built in fastload/save routines in these cartridges if they are present. That makes loading/saving tunes a whole lot faster.
Personally I'd much rather see new batches of Scannerboy's sync interface. That one was affordable as well.
Last edited by frantic (March 6, 2017 7:35 am)