CSmfDoc.h

class CSMFDoc
{
public:
CString fname;
OnSelect();
OnPlay();
};

CSmfDoc.cpp

CSMFDoc::OnSelect(){
fname = ファイル選択
}

CSMFDoc::OnPlay(){
CMainFrame* Frm = new CMainFrame;
Frm->MidiPlay(SmfName, TRUE);
}