Well Quite!

This is really not the post I wanted to write. But this is necessary information to understand the upcoming posts.

As many of you will know, and should be evident by other posts on here, I play the French Horn. The French Horn really is a family of instruments and is really quite unique in this respect, I believe. So some brief history is needed, along with an explanation of some of the standard types of Horns available.

The French Horn was originally a hunting Horn: an instrument which was worn around the body of a horseman. It had no valves and this meant that it could only play notes on the natural harmonic series dictated by the length of the instrument. The actual truth is a little more complex, and I'm not totally confident in my own understanding so I'll leave that out. Because the Horn can only play notes within a particular harmonic series, when it was used in a non-hunting context, the composer would indicate how long the instrument should be so that the player could create the right notes. This is why music throughout the Baroque and Classical periods will indicate "Horn in C", "Horn in E-flat", "Horn in Something" where Something is a key. As a piece modulates, the composer will often ask the player to change key, during the piece. This often takes some time - removing certain tubing and replacing it with different lengths. This all but eliminates the possibility of asking the Horn player to play any chromatic passage.

Around the start of the 19th century, some clever sod invented valves. This allows the player to change the length of the Horn very very quickly, without doing any plumbing at all. Slowly, people settled on a "Horn in F" - basically, 12-ft long with three valves which can be used in combination to adjust the length of the Horn from "Horn in F" right down to "Horn in B-natural" - about 15-ft long, in semi-tone steps. You may be wondering about the missing keys - F-sharp up to B-flat - these overlap with notes available from the accessible keys and so you can in fact play all the notes - except in extremis: right at the lower end of the Horn there are gaps which can not easily be sounded. Fortunately, it's very seldom that a player is required to play that low.

Now the idea was that composers should stop thinking about the harmonic series and should just write chromatically for "Horn in F". Leave it up to the Horn player to work out which fingering / which valves are actually needed for a particular note. For example, if the composer wanted the Horn to sound a G, below middle C, they should just write D (having adjusted by a fifth for the "Horn in F" bit) and then the Horn player will see that D and depress the first valve, lowering the Horn from "Horn in F" to "Horn in E-flat" which contains, in its harmonic series, the desired G (though the Horn player doesn't consciously think this. They just think, "it's a D").

However, some composers didn't get the message, and in some cases continued thinking for the Horn player, asking them to change to "Horn in E-flat" and then writing an E (following from the above example). It achieves the same effect, but in increasingly requires the Horn player to mentally rewrite the piece to "Horn in F" and then using the correct fingering. In fact, even in the 20th century, you had composers such as Richard Strauss writing his second Horn Concerto (1943) for "Horn in E-flat". I doubt anyone has ever played in on a "Horn in E-flat": almost without doubt, everyone playing it will be using a standard "Horn in F" and performing the necessary mental transposition to select the correct fingering and make the right notes sound.

So back to my original point about the family of instruments that are known as French Horns. The following are all modern French Horns:

• Single Horn in F. This is what I described above: the basic length is around 12-ft, and it has three valves that allow it to achieve the harmonic series in the keys, F, E, E-flat, D, D-flat, C and B. This is the standard starter instrument and is what I first learnt on. A good "Single F" can often be only a few hundred pounds and the instrument is reasonably light.
• Single Horn in B-flat. Because as you try and play higher, the harmonics get closer and closer together, it becomes much easier to miss the desired note and instead play a nearby harmonic. You will immediately know when this happens and it's very annoying. If you shorten the Horn then you widen the gap between the harmonics again, making it harder to hit the wrong note; the Horn feels more secure. A Horn in B-flat is 9-ft long: literally twice the length of a standard Trumpet in B-flat, and a 4th higher than the standard Horn in F. Again, it will have 3 valves which will allow it to achieve 7 keys in total, descending in semitones from B-flat through to E.
• Double Horn in F/B-flat. This is the standard Horn and what the vast majority of players will use. The instrument is a combination of both the Single Horn in F and the Single Horn in B-flat. It has one bell and one mouthpipe, but a fourth valve allows the player to select whether the B-flat side or the F side of the instrument is in use. Typically, the player will use the B-flat side almost exclusively for higher notes and the F side for lower notes, though depending on almost anything, virtually anything is possible. Almost every note will have at least two different fingerings - some of which will offer a more in-tune note or a note which is harder to miss or a fingering pattern which is easier to achieve in a fast passage.
• Alto Horn in B-flat/F. If the player is going to be playing a lot of very high notes, the security of the B-flat side is often not enough. So therefore halve the F-side to a 6-ft F-side which is now shorter than the B-flat side, making the really high notes much more secure. Note that I say secure. I do not mean easier. The source of all sound on a brass instruments in the player's lips. Regardless of the length of the instrument, the player must still make the vibrations in the lips at the correct pitch. A shorter instrument simply places the harmonics available further apart, reducing the risk that you mistakenly, given slight inaccuracies in the vibrations coming from the player's lips, play the wrong harmonic. Other than the halved F-side, the Alto is the same setup as the Double. With the decreasing length of the Horn, the ability to play low notes well deteriorates dramatically. This is really why the Alto is not that common: there are just too many pieces that demand the Horn player play reasonably low notes which are not in tune or sound pleasant on an Alto.
• Triple Horn in F/B-flat/F-alto. Yes, you saw it coming. All three instruments offering a tremendous range. It'll have at least 5, if not 6 valves and normally 5 valve levers - two of which will be operated by the thumb. Um, yeah. There are a number of problems with triples. Firstly, you have a lot of tubing, which makes them very heavy. Secondly, you really don't want the bore of the tubing (i.e. its diameter) to be the same for all three instruments: the F-alto side really should be a smaller bore in order to offer a similar resistance to the player across all three sides of the instrument. This often ends up forcing a valve very close to the mouth-piece end of the mouthpipe, which then often demands that the main tuning adjustment is directly after the mouthpiece. This then means that as you tune your Horn, the Horn moves further away or closer to the player. Oh, and they're very expensive too, simply because they demand both more material and much more labour than a standard Double.
• Double Descant in F/B-flat. Even higher. 6-ft F-side and 4.5-ft B-flat side. I.e. the B-flat side is actually the same as a Trumpet. I don't think I've ever seen one of these in the flesh. They will only be used in very certain circumstances, for example Baroque music was often written for much shorter Horns and is in fact often played on Trumpets these days as it's so screamingly high.
• There are other possibilites available too (I've not mentioned anything about "compensating" Horns). All in all, there are probably about a dozen different "standard" French Horns.

But, and this is finally my point, the composer doesn't care what the player is actually playing on, and, to a certain extent, neither does the player: the player will (almost) always think in terms of a standard Horn in F. The player will know, given a Horn in F part, how they should play any given note. The composer will write for a Horn in F. The player may be using a Single B-flat, but the player will think in terms of Horn in F, and will read the part without applying any mental transposition, but will make the correct vibrations and use the correct fingering such that the desired note will sound through some combination of achieved length and harmonic within that length.

Contrast this with Trumpets, where the composer will still, today write for Trumpet in B-flat, or C or D or whatever. Clarinets in B-flat or A or E-flat (or sometimes C). Flutes, Alto Flutes, Bass Flutes, Piccolo. Even Trombones will be explicitly written for Bass, Tenor and Alto Trombone. Thus the Horn is unique in the number of instruments that are available that are still called French Horns and the fact that the composer has long since given up caring (or in most cases understanding) about what particular type of Horn the player is using.