The Horn is the only instrument where we must take a look at how the instrument is notated. A well-versed Horn player is required to be able to transpose the different keyed parts for their instrument at sight. Players make no bones about doing this. In fact, this is a point of pride for all Hornists. However, this does not mean that you can write your Horn parts in any key willy-nilly.
As I see it, there are only two ways to notate the Horn in modern parlances. The standard one is as a transposing instrument in F all pitches sounding down a fifth. This seems common sense, except when we get to the bass clef. In older scores, when the Horn was notated in the bass clef, the transposition changed, and instead of it sounding a fifth down, it sounded a fourth up. In other words, the notation was an octave lower than today’s modern notation. There is no need for this practice to continue, and in reality, it is extinct. However, its inclusion in every orchestration text makes it confusing.
The alternative, and one I’ve never figured out why it hasn’t caught on, is to notate everything at concert pitch. If we think about it, the majority of our brass instruments, no matter their pitched key, read in concert pitch. Trombones, Euphoniums, tubas, all play in concert pitch even though their instrument is pitched otherwise. Trumpet is slowly moving over to everything in concert pitch with the prominence of the C Trumpet over the B-flat. Horn is the last holdout. What makes this interesting is that Horn is the only brass instrument without a true “family” of other instrument for the player to switch to. There’s no reason for the Horn not to be notated in concert pitch except for tradition.
Tradition brings us to our final oddity of Horn notation. Horn is the only instrument not scored for in chord order. What I mean by this is the first player plays the highest note, the second player plays the next highest, and so on, until the last player plays the lowest note. Horn doesn’t do this. Instead of the logical 1, 2, 3, 4; Horn parts are written 1, 3, 2, 4. It comes from a time when Horns were only scored for in pairs. When four Horns were scored for, it wasn’t thought of as a group of four members in the same section, rather it was thought of as two pairs of instrument that often played different parts and roles. Stray from this arrangement, and Horn players will ridicule and mock you ridiculously. It makes it more difficult for a composer to write for the Horn, because we have to remember this rule for this one instrument. The logical solution, some would think, would be to group Horns 1 and 3 on one staff, and Horns 2 and 4 on the other, but once again, Horn players scoff at this idea. Rule of thumb: odd numbered Horns are high parts/players, and even numbered Horns are low parts/players. Stray from this and suffer.
The influence of modern practices is not to be found among Horn players. Traditional is best, or so it would seem