Whereas the 1st natural is not used on the F horn (although some hornists can play it) it is very much part of the range played on the horn in high Bb and speaks well on this instrument.
The F horn’s range begins with the 2nd natural and rises to the 16th, although the naturals 12 to 16 are very difficult to play.
The instrument’s natural harmonic series can be lowered by six half steps by activating the valves, i.e. by lengthening the tube step by step.
Every activation of a valve produces a lower natural harmonic series, so the hornist has a total of seven natural harmonic series at his disposal, from which he can produce every chromatic pitch by means of overblowing. The activation of the 2nd valve, for example, lowers the horn’s pitch by a semitone, making it a horn in E; by pressing the 1st valve the player has an Eb horn, and so on.
As on the trumpet there are seven different fingerings on the horn. Each fingering lowers the natural harmonic series by a semitone:
When the lowest note is played (B1 pitch = 7th fingering) the horn’s tube length increases from 3.86 m to 5.5 m. The fact that a 5.5 m long air column has to be vibrated to sound this note means that response is harder in the lower register than in the middle and upper registers. The low notes have a low frequency and correspondingly long vibrations. In the narrow tube the amplitude cannot develop in proportion to the long vibrations, which gives the forced notes in the low register a rather rough sound.
Leaps up to the higher range can be problematical because the notes of the natural harmonic series are very close together at this level, so that even the slightest change in lip tension alters the pitch (sound production is also influenced by factors such as the instrument’s temperature or fluid in the tube). It is far easier for the hornist to attack a very high note abruptly than it is to leap from a low note to a high one.