Originally Posted by sweeks

Actually, the *pitch* doesn't change when a string is plucked (guitar, harp, etc.) or struck (piano) in different locations. The pitch (frequency) is determined by the length, tension, mass... not where the vibration is initiated. The *quality* of the note may be affected, and for a spoke I'd agree that the middle of the spoke is the best place.
Another consideration is whether the spoke is contacted by other spokes, because that will change the pitch much like pressing a guitar string against a fret.