Option Explicit 'Ver 1.0, Rick G.
Const Title = "Set Midi Volume"
If WScript.Arguments.Count Then
  If IsNumeric(WScript.Arguments(0)) Then
    SetMidi WScript.Arguments(0)
  End If
Else
  MsgBox "Argument: 0 - 100 required.",, Title
End If

Sub SetMidi(volume) ' requires wmp 7+
  Dim f, o: Set o = CreateObject("WMPlayer.OCX")
  With CreateObject("Scripting.FileSystemObject")
    f = .BuildPath(.GetSpecialFolder(2), .GetTempName & ".mid")
    .CreateTextFile(f, 1).Write _
    "MThd" & db("00 00 00 06 00 00 00 01 00 C0") & _
    "MTrk" & db("00 00 00 09 86 00 90 47 00 00 FF 2F 00") 
    o.URL = f ' open, wait while Transitioning
    Do: WScript.Sleep 100: Loop While o.playState = 9 
    ' setting now pertain to MIDI 
    o.settings.volume = volume
    o.settings.balance = 0
    o.close: .DeleteFile f
  End With
End Sub	
Function db(s) ' debug in, binary out
  For Each s In Split(s): db = db & Chr("&h" & s): Next
End Function