Tonguing is when a musician playing a wind instrument uses their tongue on the reed or mouthpiece to enunciate different notes. A silent "ta" is made when the tongue strikes the reed or roof of the mouth causing a slight breach in the air flow through the instrument.

Strictly speaking, going tuh-kuh will have conductors yelling at you, saying they can't hear the articulation (at least with the flute). With the flute, you MUST always go 'duh' on strong beats. Hence, you will get a 'duh guh duh guh' pattern when you learn to double tongue. Going 'tuh' will severely weaken the crispness of the note and blur the intended articulation.

An alteration called "double-tonguing" or "double-articulation" is used when the music being performed has many rapid notes in succession too fast for regular articulation. In this case, the tongue makes a silent "tuh-kuh." (The actual tongue positioning varies slightly from instrument. Clarinets may go "too-koo" but a bassoon may actually say "taco.") Double-articulation allows the tongue to stop the airflow twice as fast when mastered.

Tonguing is made explicit in the score by the use of accent marks, though the absence of slurs is usually understood to imply that each note should be tongued separately. When a group of notes is slurred together, the player is expected to tongue the first note of the group and not tongue any of the other notes, unless those notes have accent marks.

A more formal, but ambiguous, term for tonguing is articulation.