Voluntary use of voice in human speech and song is supported by uniquely human mechanisms of peripheral apparatus and neural adaptation to their forms. This paper examines various mechanisms of voice fundamental frequency (F0) control by laryngeal muscles based on previous reports by the author and others. Besides the well-known function of the cricothyroid, other intrinsic muscles potentially contribute to voice control by their own unique manners. Extrinsic laryngeal muscles apply horizontal and vertical forces to the laryngeal framework to enhance F0 control. The horizontal component interacts with supra-laryngeal articulators and provides causal explanation of the intrinsic vowel F0. The vertical component produces a rotation of the cricoid cartilage by means of vertical laryngeal movement along the curvature of the carvical spine. Thus, F0 is tuned by overall force balance among a number of laryngeal muscles, and our capacity of its voluntary use reflects morphological characteristics of the human larynx.
