The Silver Branch, by Rosemary Sutcliff

[silverink]

 ...[Justin] slipped free the worn shoulder strap of his instrument-case, ranged the contents on the grass beside him, and with the soft cloth in which they had been muffled, fell to burnishing the tools of his trade. Not that they needed burnishing, for he had kept them bright as glass all these long months, as though by doing so he was keeping faith with something in himself—something that was for healing and creating and making whole again, in a world that seemed to be all destroying.

—The Silver Branch pg 113