The trombone is a low brass instrument with a slide used to move between notes. Proper practice technique is the best way to quickly gain skill playing notes an octave or two above middle C on the trombone. Playing high notes on the trombone requires that you train your playing technique, including instrument position, breathing and the embouchure--the lip playing position used for brass instruments--to achieve optimal sound in high notes.
Do gentle upper-body stretches to prepare yourself for practice. These should loosen up your chest, back, hips and shoulders.
Use good breathing technique. Ensure that the lower abdominal area expands while breathing. Expanding the lower abdomen gives you extra space for air and allows you to control the stream of air using your abdominal muscles. Practice breathing with your abdomen by lying flat on your back on the floor with a book on your stomach. Attention to breath support technique is essential to reaching and maintaining high notes.
Strengthen the muscles of your lips so you can close the opening of the embouchure, called the aperture. Buzz into the mouthpiece when it is off the instruments, practicing smooth movement between high and low tones. "Buzzing," is the act of making a lip raspberry into the mouthpiece by forming the embouchure into the mouthpiece and blowing air through the lips until they buzz. Work up to the highest pitch of buzz that you can.
Play scales during warm-up. Gradually move the scales up until you enter a range that is challenging. Play as high as you can, then move back down the scale, then back up. Repeat in 15 to 20 minute intervals, resting for at least 15 to 20 minutes between sessions. Pay attention to breath support while practicing scales.
Practice higher notes than the note you aim to hit. To make sure you hit the desired high note with a solid sound, you need to extend your range past the highest note you need to play. Practicing pitches up to five whole steps higher than the target note will ensure that you nail all of your performance notes with ease.
The two factors that most affect the pitch of a trombone note are the speed of the air and the size of the embouchure aperture. Control of these two factors will lead to maximum high pitch effectiveness on the trombone.
Do not press the instrument hard into your face to get the desired note out. This technique does not lead to a sustained ability to produce high notes. Though putting lots of pressure on the lips with the mouthpiece will help you squeeze out a high note, doing this will probably hurt your lips and teeth, possibly to the point of bleeding.