The trumpet is a cylindrical-bore brass instrument that is played by the action of wind upon the lips as it passes from your lungs into the instrument. Pitch is changed both through the action of the lips as well as a system of valves that dynamically changes the length of the instrument as described below. All modern trumpets have at least three valves, and depending on the type of instrument, may have more. The vast majority of the valves found on modern trumpets are piston valves, but rotary-valve horns are still in active use by professional orchestras in America and around the world, and are still made and produced today by manufacturers such as Scherzer Trumpets and Schagerl Trumpets.
Method of Playing 
The playing method is rather simple. Wind is blown through the lips (formed into what is called an embouchure) into the instrument through a mouthpiece. The natural vibration of the lips causes a standing wave to be set up inside the horn, which creates the sound according to the harmonic series (see the corresponding article on Wikipedia for more information on this concept in physics). For a trumpet tuned in Bb, the overtone series(in actual pitch, not written) would be Bb2 (the fundamental), Bb3, F4, Bb4, D5, F5, Ab5, Bb5, C6, D6, F6, and so on. The harmonic series derives from the physics of standing waves in a open tube. The actual pitches that are available are entirely dependent on the length of the tubing. However, for a given tube length, the harmonic series would follow the same pattern. All military bugle calls are achieved with this same series of notes. Modern chromatic trumpets play other notes by use of valves which allow the player to dynamically adjust the tube-length of the trumpet, enabling the use of the full chromatic scale.
The Valve Pattern 
Most modern trumpets use three valves. Each valve, alone and in combination, modifies a given overtone note according to the following pattern. The first valve, played by the right hand index finger, modifies notes by lowering them two half steps (or a whole). The second valve, played by the right hand middle finger, lowers notes by a single half step. The third valve, played by the right hand ring finger, lowers notes by three half steps. Combinations of these valves simply add their respective modifications. For example, the first valve plus the second valve will lower the note by three half steps. The second valve plus the third will lower the overtone note by four half steps.
In this manner, the trumpet is capable of producing every note of the chromatic scale.
The following lists the valve fingering combination for the descending C chromatic scale starting on middle C.
|Note||Valves||Half steps below each overtone|
|G4||101 or 000||5||0|
Note that there can be overlap from any given transposition from an overtone series note. These are called "alternate fingerings" and can be played for various musical effects. However, alternate fingerings (and even some standard fingerings) have intonation issues that need to be addressed.
- ITG Journal, March 2004, pg. 53
- Burt, Jack. "The Rotary Trumpet: An Introduction." ITG Journal, March 2004, pp. 52-55