Three rotary valves control the flow of air in the single horn, which is tuned to F or less commonly B-flat. The more common double horn has a fourth valve, usually operated by the thumb, which routes the air to one set of tubing tuned to F or the second set of tubing tuned to B-flat. Triple horns with five valves are also made, tuned in F, B-flat, and a descant F (one octave above the lower F).
A musician who plays the horn is called a horn player (or, less frequently, a hornist). The International Horn Society has recommended since 1971 that the instrument itself be properly referred to solely as the horn.
Today, music for the horn is typically written in F (or sometimes, notably in British bands, in E-flat), and sounds a perfect fifth lower than written (or a major sixth lower for the E-flat horn). The limitations on the range of the instrument are primarily governed by the available valve combinations for the first four octaves of the overtone series and after that by the ability of the player to control the pitch through their air supply and embouchure. The typical written ranges for the horn start at either the F-sharp immediately below the bass clef or the C an octave below middle C.
The standard range starting from a low F-sharp is based on the characteristics of the single horn in F. However, there is a great deal of music written beyond this range on the assumption that players are using a double horn in F/B-flat. This is the standard orchestral instrument and its valve combinations allow for the production of every chromatic tone from two octaves on either side of the horn's written middle-C (sounding F two octaves below the bass clef to F at the top of the treble clef). Although the upper range of the horn repertoire rarely exceeds high C (two octaves above the horn's middle C, sounding F at the top of the treble clef), skilled players can achieve yet higher pitches.
Also important to note is that many pieces from the Baroque to Romantic periods are written in keys other than F, with the player providing the final transposition to the correct pitch. This practice began in the early days of the horn before valves, when the composer would indicate the key the horn should be in (horn in D, horn in C, etc.) and the part would be notated as if it were in C. For example, a written C for horn in D would be transposed down a minor third and played as an A on F horn. This tradition was only recently abandoned, being used as late as Wagner and Richard Strauss, albeit only for short passages (the majority of the piece being written for horn in F).
Early horns were much simpler than modern horns. These early horns were brass tubes with a slightly flared opening (the bell) wound around a few times. These early "hunting" horns were originally played on a hunt, often while mounted, and the sound they produced was called a recheat. Change of pitch was effected entirely by the lips (the horn not being equipped with valves until the 19th century). Without valves, only the notes within the harmonic series are available. The horn was used, among other reasons, to call hounds on a hunt and created a sound most like a human voice, but carried much farther.
In orchestral settings, the horn (or, more often, pairs of horns) often invoked the idea of the hunt, or, beginning in the later baroque, determined the character of the key being played or represented nobility, royalty, or divinity.
Early horns were commonly pitched in B-flat alto, A, A-flat, G, F, E, E-flat, D, C, and B-flat basso. Since the only notes available were those on the harmonic series of one of those pitches, they had no ability to play in different keys. The remedy for this limitation was the use of crooks, i.e. sections of tubing of differing length that, when inserted, altered the length of the instrument, and thus its pitch.
Orchestral horns are traditionally grouped into "high" horn and "low" horn pairs. Players specialize to negotiate the unusually wide range required of the instrument. Formerly, in certain situations, composers would call for two pairs of horns in two different keys; for example, a composer might call for two horns in C and two in E-flat for a piece in c minor, in order to gain harmonics of the relative major unavailable on the C horns. Eventually, two pairs of horns became the standard, and from this tradition of two independent pairs, each with its own "high" and "low" horn, came the modern convention of writing the 1st and 3rd parts above 2nd and 4th.
In the mid-18th century, horn players began to insert the right hand into the bell to change the length of the instrument, adjusting the tuning up to the distance between two adjacent harmonics depending on how much of the opening was covered. This technique, known as hand-stopping, is generally credited to Anton Joseph Hampel around 1750, and was refined and carried to much of Europe by the influential Giovanni Punto. This offered more possibilities for playing notes not on the harmonic series. By the early classical period, the horn had become an instrument capable of much melodic playing. A notable example of this are the four Mozart Horn Concerti and Concert Rondo (K. 412, 417, 477, 371), wherein melodic chromatic tones are used, owing to the growing prevalence of hand-stopping and other newly-emerging techniques.
Around 1815 the use of pistons (later rotary valves) was introduced, initially to overcome problems associated with changing crooks during a performance. At first, however, valves were slowly adopted in the mainstream because of unreliability, musical taste, and players' distrust, among other reasons. Many traditional conservatories and players refused to transition at first, claiming that the valveless horn, or "natural horn", was a better instrument. Some musicians, specializing in period instruments, still use a natural horn when playing in original performance styles, seeking to recapture the sound and tenor in which an older piece was written.
However, the use of valves opened up a great deal more flexibility in playing in different keys; in effect, the horn became an entirely different instrument, fully chromatic for the first time. Although, valves were originally used primarily as a means to play in different keys without crooks, not for harmonic playing. That is reflected in compositions for horns, which only began to include chromatic passages in the late 19th century. When valves were invented, generally, the French made smaller horns with piston valves and the Germans made larger horns with rotary valves. It is the German horn that is erroneously referred to in the English language (and more commonly in the United States and Canada) as the French horn. There is not a clear consensus on the reason or reasons for this nomenclature, and, as there are conflicting proposals, more research is necessary.
Despite the introduction of valves, the single F horn proved difficult for use in the highest range, where the partials grew closer and closer, making accuracy a great challenge. An early solution was simply to use a horn of higher pitch—usually B-flat. The use of the F versus the B-flat horn was a hotbed of debate between horn players of the late nineteenth century, until the German horn maker Ed. Kruspe produced a prototype of the "double horn" in 1897.
The double horn also combines two instruments into a single frame: the original horn in F, and a second, higher horn keyed in B-flat. By using a fourth valve (usually operated by the thumb), the horn player can quickly switch from the deep, warm tones of the F horn to the higher, brighter tones of the B-flat horn. The two sets of tones are commonly called "sides" of the horn. Using the fourth valve not only changes the basic length (and thus the harmonic series and pitch) of the instrument, it also causes the three main valves to use proportionate slide lengths.
In the USA, the two most common styles ("wraps") of double horns are named Kruspe and Knopf, after the first instrument makers who developed and standardized them. The Kruspe wrap locates the B-flat change valve above the first valve, near the thumb. The Knopf wrap has the change valve behind the third valve, near the pinky finger (although the valve's trigger is still played with the thumb). In effect, the air flows in a completely different direction on the other model. Kruspe wrap horns tend to be larger in the bell throat than the Knopf type. Typically, Kruspe models are constructed from nickel silver or German Silver, while Knopf type horns tend to be of yellow brass. Both models have their own strengths and weaknesses, and while the choice of instrument is very personal, an orchestral horn section is usually found to have either one or the other, owing to the differences in tone color, response, and projection of the two different styles.
In the UK and Europe the most popular horns are arguably those made by Gebr. Alexander, of Mainz (particularly the Alexander 103), and those made by Paxman in London. In Germany and the Benelux countries, the Alex. 103 is extremely popular. These horns do not fit strictly into the Kruspe or Knopf camps, but have features of both. Alexander prefers the traditional medium bell size, which they have produced for many years, whereas Paxman do offer their models in a range of bell throat sizes. In the United States, the Conn 8D, a mass produced instrument based on the Kruspe design, has been extremely popular in many areas (New York, Los Angeles, Cleveland, Philadelphia). Since roughly the early 1990s, however, for reasons ranging from changing tastes to a general dislike of Conn's newer 8Ds, orchestras have been moving away from the popular Conn 8D. Knopf model horns (by Geyer, Karl Hill, Keith Berg, Steve Lewis, Dan Rauch, and Ricco-Kuhn) are used in other areas (San Francisco, Chicago, Pittsburgh, Boston, Houston).
The Vienna horn is a special horn used primarily in Vienna, Austria. Instead of using rotary valves or piston valves, it uses the Pumpenvalve (or Vienna Valve), which is a double-piston operating inside of the valve slides, and usually situated on the opposite side of the corpus from the player's left hand, and operated by a long pushrod. Unlike the modern horn, which has grown considerably larger internally (for a bigger, broader, and louder tone), and considerably heavier (with the addition of valves and tubing in the case of the double horn) the Vienna horn very closely mimics the size and weight of the natural horn, (although the valves do add some weight, they are lighter than rotary valves) even using crooks in the front of the horn, between the mouthpiece and the instrument. Although instead of the full range of keys, Vienna horn players usually use an F crook for most music, switching to an A or B-flat crook for higher pitched music (Beethoven 7th symphony, Bach, various Mozart and Haydn, etc). Vienna horns are often used with funnel shaped mouthpieces similar to those used on the natural horn, with very little (if any) backbore and a very thin rim. The Viennese horn requires very specialized technique and can be quite challenging to play, even for accomplished players of modern horns.
Sometimes, a derivative of the F alto horn, commonly used in brass bands and marching bands, called a mellophone is used. It is shaped like a trumpet, with piston valves played with the right hand and a forward-pointing bell. These horns are generally considered better marching instruments than regular horns because their position is more stable on the mouth, they project better, and they weigh less. Though they are usually played with a trumpet like mouthpiece, their range overlaps the common playing range of the horn. This mouthpiece switch makes the mellophone louder, less mellow, and more brassy and brilliant, making it more appropriate for marching bands. It is a sound similar to that of the bass trumpet.
As they are pitched in F and their range overlaps that of the horn, mellophones can be used in place of the horn in brass and marching band settings. Sometimes, however, mellophones are unpopular with horn players because the mouthpiece change can be difficult and requires a different embouchure. Mouthpiece adapters are available so that a horn mouthpiece can fit into the mellophone lead pipe, but this does not compensate for the many differences that a horn player must adapt to. The bore is generally cylindrical as opposed to the more conical horn; thus, the "feel" of the mellophone can be foreign to a horn player. Another unfamiliar aspect of the mellophone is that it is played with the right hand instead of the left. Intonation can also be an issue when playing the mellophone.
In orchestral concerts, regular concert horns are normally preferred to mellophones because of their tone, which blends better with woodwinds and strings, and their greater intonational subtlety—since the player can adjust the tuning by hand. For these reasons, mellophones are played more usually in marching bands and brass band ensembles, occasionally in jazz bands, and almost never in orchestral settings.
While horn players may be asked to play the mellophone, it is unlikely that the instrument was ever intended to be used as a substitute for the horn, mainly because of the fundamental differences described.
The Wagner tuba is a rare brass instrument that is essentially a horn modified to have a larger bell throat and a vertical bell. Contrary to intuition, it is generally not considered part of the tuba family. Invented for Richard Wagner specifically for his work Der Ring des Nibelungen, it has since been written for by various other composers, including Bruckner and R. Strauss. It uses a horn mouthpiece and is available as a single tuba in B-flat or F, or, more recently, as a double tuba similar to the double horn. Its range is similar to that of the euphonium.
The horn, although not large, is awkward in its shape and does not lend itself well to transport, especially transport on commercial airlines. To compensate, horn makers can make the bell detachable. This allows for smaller and more manageable horn cases. The player can attach the bell when performing. This also allows for different bells to be used on the same horn, somewhat alleviating the need for multiple horns for different styles.
The horn is most often used as an orchestral instrument, with its singular tone being employed by composers to achieve specific effects. Leopold Mozart, for example, used horns to signify the hunt, as in his Jagdsinfonie (hunting symphony). Once the technique of hand-stopping had been developed, allowing fully chromatic playing, composers began to write seriously for the horn. Telemann wrote much for the horn, and it features prominently in the work of Handel and in Bach's Brandenburg Concerto no. 1. Gustav Mahler made great use of the horn's uniquely haunting and distant sound in his symphonies, notably the famous Nachtmusik (night music) section of his Symphony No. 7.
Many composers have written just one or a few notable works which have become established as favorites in the horn repertoire; this includes Poulenc (Elegie) and Saint-Saëns (Concertpiece for horn and orchestra, op. 94 and Romance). Others, particularly Mozart, whose friend Joseph Leutgeb was a noted horn player, wrote extensively for the instrument including concerti and other solo works. Mozart's A Musical Joke satirizes the limitations of contemporary horn playing, including the risk of selecting the wrong crook by mistake. By the end of the 18th Century the horn was sufficiently established as a solo instrument that the horn player Giovanni Punto became an international celebrity, touring Europe and inspiring works by composers as significant as Beethoven.
The development of the valve horn was exploited by romantic composers such as Richard Strauss, Bruckner and Mahler. Strauss's Till Eulenspiegel's Merry Pranks contains one of the best known horn solos from this period, relying on the chromatic facility of the valved horn.
Horn music in England had something of a renaissance in the mid 20th Century when Dennis Brain inspired works such as Britten's Serenade for Tenor, Horn and Strings and other works from contemporary composers such as Michael Tippett, who stretches horn ensemble playing to its technical limits in his Sonata for Four Horns. Peter Maxwell Davies was commissioned by 50 amateur and professional UK horn players to write a horn piece to commemorate the 50th anniversary of Brain's death.
Much of the repertoire is scored as featured parts for the orchestral players, especially the principal horn. It is common for leading horn players to move from principal positions in the great orchestras to distinguished solo careers, a path followed by Brain and many since.
There is an abundance of chamber music repertoire for horn. It is a standard member of woodwind quintet instrumentation and often appears in other configurations, such as Brahms' "Horn Trio" for violin, horn and piano. Also, the horn can be used by itself in a horn ensemble or "horn choir." The horn choir is especially practical because the extended range of the horn provides the composer or arranger with more possibilities, registerally, sonically, contrapuntally, etc.
Composer Daniel Bickerton (Cardiff University, Wales / Trinity College of Music, London) has written several pieces for horn which explore the integration of elements from the worlds of jazz and rock music into an original contemporary musical language. The purpose of his work is an attempt to situate the classically-associated horn within a jazz/rock-inspired context writing for the instrument to its full potential in terms of range, register and use of extended techniques. His work When The Stakes Are High written in 2008 (for horn & piano accompaniment) demonstrates this concept.
This setup of high-low-high-low has many reasons: Firstly, it makes it easier to play a high part if you have someone on your left playing a low part, but it makes it easier to play a low part if you have your high player (from your pair) to your left. Secondly, pairing makes it easier to write for horns, seeing as the 3rd & 4th horns can take over from the 1st & 2nd horns, or play a contrasting part. Thirdly, when music was first written, it was for the Natural horn, which meant that the horns could only easily play certain notes. Because of this, the 1st & 2nd horns had to be in a different key from the 3rd & 4th horns so that more of the notes can be played. For example, if the piece is in C minor, the 1st & 2nd horns might be in C, the tonic major key, which could get most of the notes, and the 3rd & 4th horns might be in E flat, the relative major key, to fill in the gaps.
Most horn sections today also have an assistant who doubles the 1st horn part for selected passages joining in loud parts, playing instead of the principal if there is a 1st horn solo approaching, or alternating with the principal if the part is tiring to play. Playing assistant is usually overlooked, but it is harder than it seems, and takes experience to do it well. Often the assistant is asked to play a passage after resting a long time. Also, he or she may be asked to enter in the middle of a passage, exactly matching the sound, articulation, and overall interpretation of the principal. The assistant is occasionally referred to as a "bumper".
Some pieces (like Rachmaninov's Isle of the Dead, Britten's Sinfonia da Requiem, Holst's The Planets and Richard Strauss' Don Quixote) have called for 6 horns, or even 8 horns (e.g., some of Mahler's Symphonies and Wagner's operas). Here the pairing remains the same, with the odd horns being high parts and the even horns being low parts.