This seems to work but may need some tweaking with the Sleep, delays

Code:
#NoEnv
#SingleInstance Force

dir:= "E:\bb\Drums2"

Loop Files, %dir%\*.MGU, R  ; Recurse into subfolders.
 {

  WinActivate, ahk_class TBandWindow
  WinMenuSelectItem, ahk_class TBandWindow, , File, Open
  WinWait, ahk_class #32770
  Sleep, 2000
  SendRaw, %A_LoopFileFullPath%
  Sleep, 2000
  Send, {ENTER}
  Sleep, 3000
  Send, !2  : Solo Melody
  Send, !8  : Solo Melody
  Sleep, 1000
  ;MsgBox, Save
  WinActivate, ahk_class TBandWindow
  WinMenuSelectItem, ahk_class TBandWindow, , File, Save Special, Save Song as MIDI File
  WinWait, ahk_class TMIDIexportDlg
  Sleep, 2000
  Send, {ENTER}
  WinWait, ahk_class #32770
  Sleep, 3000
  Send, {ENTER}

  Sleep, 2000


  if WinExist("ahk_class TxForm") or WinExist("ahk_class" Overwrite file?)
  {  
     ;MsgBox, Overwrite?
	 WinActivate, ahk_class Overwrite file? ;TxForm
     ;Sleep, 500
     Send, y
	 ;WinWaitClose, ahk_class TxForm
  }
 

  Sleep, 1000
  Send, !{F4}
  Sleep, 2000