The lip position and pressure, shaping of the vocal tract, choice of reed and mouthpiece, amount of air pressure created, and evenness of the airflow account for most of the clarinetist's ability to control the tone of a clarinet. A highly skilled clarinetist will provide the ideal lip and air pressure for each frequency (note) being produced. They will have an embouchure which places an even pressure across the reed by carefully controlling their lip muscles. The airflow will also be carefully controlled by using the strong stomach muscles (as opposed to the weaker and erratic chest muscles) and they will use the diaphragm to oppose the stomach muscles to achieve a tone softer than a forte rather than weakening the stomach muscle tension to lower air pressure. Their vocal tract will be shaped to resonate at frequencies associated with the tone being produced.