In order that your voice may respond quickly to change of pitch and words, it must have considerable flexibility. The development of a technique which permits you to make vocal adjustments rapidly and precisely gives lightness to tone which is desirable and necessary either in singing a slow, sustained song or a fast, staccato one.
Perhaps your voice may not have natural flexibility. Nevertheless, you should strive to acquire it as much as possible. Practice scales and arpeggios slowly at first, gradually increasing the tempo as you gain skill. Whatever the rate of speed, the tone should always be smooth and easily produced, the pitch exact and true, and the time and rhythm correct and flowing.