Play the chalameau A located in the middle of the staff. This note is played by leaving all of the keys open, except for the key directly on top of the left index finger's natural resting point on the upper joint.
Hold the fingering for A and add the register key that sits above your left thumb. This will play chalameau B flat.
Depress all of the main keys, including the register key and depress the left pinky register key. This will give you clarino B natural.
Practice Step 1 to 3 by holding each note for about four seconds. Use caution to keep your breath support firm and your embouchure loose. Players who tense up when moving from B flat to B will emit a squeaking noise or produce a pale, thin sound.
Increase the speed by playing quarter notes at about one second per note. Alternate only between B flat and B, the two notes that create the most difficulty.