Natural horn
Valveless horn of the early Classical period.
What it means
The natural horn is a horn without valves. It has only the notes of its harmonic series, whose fundamental can be changed by attachable crooks: with a longer crook the instrument stands lower, with a shorter one higher. This allowed it to be adapted to the key of a movement, which appears in scores of the eighteenth and early nineteenth centuries as a pitch indication — for instance horn in E♭ or in D. The right hand in the bell supplies notes outside the series and at the same time changes the tone colour.
Musical use
The music for this instrument is shaped by its limitation: fanfare-like triadic figures in the low register, melodic leading only in the high register, where the natural notes lie densely, and a mixture of colour from open and stopped notes. Composers of the Viennese Classical period write deliberately so that the available notes remain sustaining and the stopped notes stand at a suitable place. With the introduction of valves in the nineteenth century the horn became chromatic, and the character of the parts changed; the transition took place over decades, and some composers deliberately still wrote for the natural instrument. In historically informed performance practice it is common again today.
Performance practice
Everything depends on embouchure and tonal conception, for there are no valves to help; practise slurs across the natural notes until you hear the series securely. Hand position in the bell is a chapter of its own: it regulates intermediate notes, intonation, and colour, and must be learned for every note. Expect volume differences between open and stopped notes and balance them through the air without blurring the colour — it belongs to the style. Choose the crook that fits the key and tune after warming up. Practise quietly, because the instrument becomes uncontrollable under pressure.
Bear in mind that the choice of crook belongs to preparation: it determines the fundamental and the tonal character, and a change during the work needs time that must be planned for. Check in the score which pitches are called for.