MSDN says :
This structure provides the ability to play MIDI files within Microsoft® Windows® CE. This structure inputs MIDI information as a special WAV format.

typedef struct _WAVEFORMAT_MIDI{
WAVEFORMATEX wfx;
UINT32 USecPerQuarterNote;
UINT32 TicksPerQuarterNote;
} WAVEFORMAT_MIDI, *LPWAVEFORMAT_MIDI;
But,how to play ....?????
Microsoft is kidding me.