Jump up ^ This sequence of fifths features the diminished fifth (b,f), which replaces the perfect fifth (b,f♯) containing the chromatic note f♯, which is not a member of the C-major key. The note f (of the C-major scale) is replaced by the note f♯ in the Lydian chromatic scale (Russell, "The fundamental harmonic structure of the Lydian scale", Example 1:7, "The C Lydian scale", p. 5).
Guitars have been played since the Renaissance era, after descending from the ancient Greek instrument, the kithara. Or, at least, that's how the theory goes: the only real proof for this is the similarities between the Greek word and the Spanish word, quitarra. Early guitars often had four strings, evolving into the six-string version we know today in the late 1600s. Anton Stradivari, the famous violin-maker, also had a hand in making guitars. There's now only one Stradivarius guitar left in existence.