Karabiner: volume to shift+option+volume

private.xml

<?xml version="1.0"?>
<root>
    <item>
        <name>volume to shift+option+volume</name>
        <identifier>private.volume_to_shift_option_volume</identifier>
        <autogen>
            __KeyToKey__
            ConsumerKeyCode::VOLUME_UP,
            ConsumerKeyCode::VOLUME_UP, ModifierFlag::SHIFT_L | ModifierFlag::OPTION_L
        </autogen>
        <autogen>
            __KeyToKey__
            ConsumerKeyCode::VOLUME_DOWN,
            ConsumerKeyCode::VOLUME_DOWN, ModifierFlag::SHIFT_L | ModifierFlag::OPTION_L
        </autogen>
    </item>
</root>