One of the fundamentals of singing is to understand that singing is of a particular duration.
One sings a pitch and it is going to be sustained for some length of time, whether that be a little time or a long time. The value of a Sustaining Exercise with the singer sustaining the pitch for longer amounts of time is an increased:
Of course, a sustaining exercise on one pitch can be combined with movement up and down the scale. Then, the focus will also include how to sing a legato line and create beautiful musical phrases!