Since the music piece is a battery operated piece I would not wash it at all. The battery will eventually wear down and then you can removed the dead battery, sew it closed, and have a safe toy again. These types of toys are not meant to be washed. With the musical piece inside. Your idea of taking it out and putting it back in with velcro for future sound box replacement is good. I am not sure about what stuffing is in this kind of toy. It may not be washable. I would say not to put it in the washer. Hand washing the outside with a rag and some oxyclean may be a good bet.