Another curious Richard Strauss quote "If you can just barely hear the (French) horns on stage, the balance is perfect." Strauss clearly loved the horn - he wrote two concertos and his orchestral music is filled with famously difficult and copious horn writing. If he just barely wanted to hear the horns, why did he write 8 horn parts in Ein Heldenleben?
The horn is the instrument that holds it all together in our ensemble - it is capable of incredible range, virtuosic technique, a variety of tone colors, and the ability to blend easily with other instruments. It produces a prototypical conical sound.
As I mentioned in ..."why just 2 horns" when we formed the Boulder Brass in the early 90's, we relied heavily on the Philip Jones Brass Ensemble library for programming because there was practically no music written for our instrumentation. The PJBE / London Brass is 4 trumpets, 1 horn, 4 trombones & tuba. We would often double the horn part just to give the horn a fighting chance to be heard on stage. The realization that one horn: 1) just isn't enough sound to balance the ensemble; and 2) unnecessarily limits some scoring possibilities; led to some scoring techniques for horn when writing music for our unique instrumentation. I'll only list them here because each technique could easily be (and likely will be) its own blog entry.
As a solo line, with careful attention to the weight of the accompaniment
As a solo line, doubled (2 horns) with less careful accompaniment
Doubled (unison or at the octave) with a brighter instrument to add weight and/or soften the edges (I love piccolo trumpet and horn written in octaves).
A melodic or counter melodic line written in octaves - to my ears this more than doubles the power potential
As a harmonic pad - sustained sounds in a brass ensemble can overwhelm a solo melodic line. Use of horns for this purpose (instead of trombones, for example) mitigates the "harmonic cloud"
As the top voices in a warm sounding conical choir (horns, euphonium, tuba)
As the middle voices in a different choir (flugelhorn, horns, euphonium)
In an even larger conical context - 2 flugelhorns, horns, euphonium, tuba
I like to interlace horns in a chord by writing the trombones in an open chord leaving open chord positions for the horns, either within the chord, or one inside and one on top.
As the bass voice for a larger ensemble - I don't do this enough, and really like that sound.
As the bass voice in a treble choir.
You get the idea - the possibilities are nearly endless, but this covers the high points. I'll talk more about voicing and colors later.