Various embodiments relating to resonance inspections and in-service parts are disclosed. One protocol (150) includes conducting a resonance inspection of an in-service part (152). The frequency response of the in-service part may be compared with a resonance standard (154) for purposes of determining whether or not the in-service part is changing abnormally (156). An in-service part that is identified as changing abnormally may be characterized as being “rejected” (160). An in-service part that is no identified as changing abnormally may be characterized as being “accepted” (158).