Int 66 Fn 0704  - Midpak - Register Xmidi                                  [s]

   AX = 0704h
   CX:BX -> XMIDI sequence data
   DI:SI = length of XMIDI data

Return: AX = status
       0000h unable to register XMIDI data
       0001h XMIDI file registered resident
       0002h XMIDI file was registered to the application