The SCP would be a silver fork, ornamental in design. When placed on or near any instrument, the instrument becomes anomalously tuned over a period of time depending on 1) distance between object and instrument 2) complexity of the instrument, and 3) how out of tune the instrument was. In addition, a subject who eats with the fork becomes able to sing more on-key and with greater range. Possible tests could be radio signals, corrupted audio files, or off-key recordings of music (digital, CDs, records).
The origin I'm thinking of is that it was anonymously sent to Dr. Clef (because music jokes). A letter included would read "To Ukulele Man - May your name sound clear" (referencing Dr. Clef's file where he says his true name is an A chord on a ukulele). However since Dr. Clef is a complex and established character, I'd be willing to drop this idea if it would be too difficult to write.
Thoughts? Suggestions? Is the idea really stupid? Whatever kind of feedback you leave, thanks.