Antique instruments of all ages can be restored provided they are, or can be made to be, structurally sound and that restoration will not result in the permanent loss of any important evidence. It is not always possible or desirable to restore them to playing condition. More modern instruments are sometimes in need of extensive overhaul, for instance to replace strings made from historically inauthentuc materials (such as steel or phosphor bronze). Sometimes plactic jacks and their poor quality machine made registers need to be replaced as they deteriorate with age. Usually wooden jacks and properly made registers can be substituted. Failed joints can be re-glued and soundboard splits repaired. Occasionally a whole soundboard may need to be replaced. Keyboards can be altered to allow transposition.