Here are many of the useful articulations for the horn, explained and demonstrated by concert professionals.
Notes played without tonguing. Legato means 'smoothly'. Notation is a curved line above or below the notes. The line is called a 'slur' and indicates that the notes should be played legato, which is often called slurred. The first note in a legato group is always tongued.
Non Legato or 'Tongued'
Each individual note tongued and separated. The technique used by horn players for separating the notes is called 'tonguing'. As the player blows, the tip of the tongue touches the roof of the mouth just behind the front teeth. This is done by a very quick movement a little like saying the letter 't'. The tongue briefly disrupts the flow of air into the instrument creating a slight separation between the notes. Some players use a different technique which involves tonguing between the teeth.
Short and separated notes (all tongued). The notations are dots above or below the notes. Staccato notes can be created by returning the tongue to it's position behind the front teeth very soon after the note has begun, so cutting off the flow of air. In playing the example shown (left) the movement of the tongue would be similar to saying, 'tut, tut, tut' whilst blowing.
Very short notes. Literally translated - as short as possible. Notated either with wedge shapes above the notes as shown (left) or sometimes ordinary staccato dots are used along with a written instruction staccatissimo. Staccatissimo technique is virtually the same as staccato. The main difference is that because the note is very short, players tend to blow a little more air through in order for the note to 'speak' clearly. This also has the effect of giving the sound more 'attack'.
A hard attack to the start of the note, notated by upward pointing wedges above the notes.
Legato tonguing is very gentle tonguing - a very slight separation between the notes - almost legato. There are two different types of notation for legato tonguing. The staccato and slur combination implies a lighter touch like staccato notes that almost join together, whereas the tenuto and slur combination suggests longer sounds with only the very gentlest use of the tongue to separate them. Players interpret these symbols in different ways. Watch the video clips for a brief explanation.
Double and Triple Tonguing
Compound tonguing in groups of two or three. The notation example shown is often used to indicate double and triple tonguing, but players will often use the technique to play passages of notes that may be written as ordinary tongued or staccato notes. Double tonguing requires the player to form syllables with their toungue whilst blowing such as 'ta-ka, ta-ka, ta-ka' (or possibly 'da-ka') in order to create very rapid articulation. Triple tonguing would involve repeating a pattern such as 'ta-ka-ta' to group notes in threes.
A rolled 'r' tonguing. Not all players can do flutter tonguing. Those that cannot have to 'fake' with a throat flutter that sounds less effective, more of a rumbling sound than a crisp 'rrrrrrrrrrrr'.