I had exactly this problem and I had to do some registry wrangling to solve it. Firstly go to HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Control\Class. You see lots of apparently random collections of numbers and letters. There are multiple entries for {4d36e96c-e325-11ce-bfc1-08002be10318}. Find the one that contains a REG_SZ value called "Class" with value "MEDIA":
Expand this key out and you'll see several keys each with 4 digits. All of them will have a Drivers key, some of them a midi key below that. Identity all that do and write down the value of the subkey below that. In my case mine is called "KORGUM64.DRV":
Now this is where we need to be super careful. We need to add a String value called "Alias" under each of the keys which end .DRV. The first one needs to be set to midi, the 2nd midi1 the 3rd midi2 etc. Write down exactly which is which as we'll need it for the next step. Some will have the same value (probably wdmaud.drv) don't worry about that - just crack on!
Finally navigate to HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows NT\CurrentVersion\Drivers32 and add new string values with the names midi, midi1 midi2 etc. and the driver values you had from before:
If you use 32 bit software you may also need to add exactly the same value at HKEY_LOCAL_MACHINE\SOFTWARE\WOW6432Node\Microsoft\Windows NT\CurrentVersion\Drivers32