-- Set the full document as a region
local fulldocregion = finale.FCMusicRegion()
fulldocregion:SetFullDocument()
-- Get the selected region
local region = finenv.Region()
-- Loop through all staves in the full document
for slot = fulldocregion.StartSlot, fulldocregion.EndSlot do    
    -- Convert from slot number to staff number/ID
    local staffnumber = region:CalcStaffNumber(slot)
    -- Load staff object
    local staff = finale.FCStaff()  
    staff:Load(staffnumber)
    -- Create a FCInstrumentPlaybackData object for the staff
    local playbackdata = staff:CreateInstrumentPlaybackData()
    -- Go through all 4 layers and process the note layer
    for layer = 1, 4 do
        local layerdef = playbackdata:GetNoteLayerData(layer)
        -- Mute in region, play outside region
        layerdef.Play = not region:IsStaffIncluded(staffnumber)
    end
    -- Save the playback settings
    playbackdata:Save()
end