Kenny Dorham: "Kenny Dorham was well known for his quiet, subdued sound. He could play as high and as fast as other trumpet players, but his sound was much softer, earning him the nickname of 'Quiet Kenny.'
His sound had a lot to do with his embochure. You can hear that he plays with his tongue high in his mouth, getting a thin sound. Also, he uses primarily upper air, almost never supporting his sound with lower air.
The combination of the high tongue and lack of lower air support made the sound very light, thin, and soft, giving him the sound that we easily recognize as Kenny Dorham."