Comment:  The voice is freer and therefore able to be more flexible, rhythmic, and have more musical nuances.

Quote: The substance of an effective performance is rhythm. Rhythm is inseperable from tempo (movement) and is instrumental in tracing the design of a musical phrase. It is also a factor in tone quality, since the vibrato oscillates in rhythmic patterns. Rhythm, synonymous with movement, is also associated with emotional expression. Thus, tempo, phrasing, tone quality and emotion may be said to possess a rhythmic essence from which the character of each is derived and without which vocalization would be empty and meaningless. (Voice: Psyche and Soma)