public DoubleProperty balanceProperty ()

taken from field

The relative left and right volume levels of the clip. Valid range is -1.0 to 1.0 where -1.0 gives full volume to the left channel while muting the right channel, 0.0 gives full volume to both channels and 1.0 gives full volume to right channel and mutes the left channel. Values outside this range are clamped internally.