F+ (pitch)
F+ is a musical pitch approximately 20 cents sharp of modern concert F, and is primarily associated with the Northumbrian smallpipes.
Similarly, composer Ben Johnston uses a "−" as an accidental to indicate a note is lowered 21.51 cents, or a "+" to indicate a note is raised 21.51 cents. 498.04 + 21.51 = 519.55.
