 By combining a long length with a narrow bore, the French horn's design allows the player to easily reach the higher overtones which differ by whole tones or less, thus making it capable of playing melodies before valves were invented.Early horns were commonly pitched in B alto, A, A, G, F, E, E, D, C, and B basso.Since the only notes available were those on the harmonic series of one of those pitches, they had no ability to play in different keys.