Multiple tonguing is an advanced
trumpet playing technique. During normal playing, blowing air through the horn produces sound, and "notes" are produced by stopping that air using the tip of your tongue. Visualizing the syllable “ta”, where the tip of the tongue taps the roof of the mouth near the gums, does this. However, single tonguing (as this is called) has limits to speed. The tip of your tongue can only tap so fast, and therefore can produce only so many notes. This is where multiple tonguing comes into play.
Multiple tonguing is a technique often wholly unknown to younger players. It involves the use of the back of the tongue as well as the tip. There are two kinds: double tonguing and triple tonguing. Triple tonguing is taught first:
The sounds produced are "tu tu ku", "tu ku tu" or "ku tu tu" the first of which is most common. The back of the tongue strikes the roof of the mouth near the back just after the tip strikes the front, utilizing a sort of see-saw motion to gain speed. In order to get high notes, the sound may be visualized as “te te ke”.
Double tonguing is triple tonguing minus one “tu”. In other words, you go “tu ku tu ku”. This gives speed, but is hard on less experienced players for whom the “ku” sound is unnatural.
Multiple tonguing is the method used by professionals that most astounds audiences. The amazing speed in some compositions (Carnival of Venice, etc.) seems unreal. With practice, most players can get amazing speed too.
The best way to learn multiple tonguing is with the aid of a private teacher. I learn from the trumpet bible, “Arban’s Complete Conservatory Method For Trumpet” with the help of a teacher.