Anecdotally, music therapists tend to have limited facility with their expression hand. This played out amongst MM participants. Some struggled to establish confident quaver rhythms with consistent up and down strums, most were unable to use accents, rests or other elements of variation to create light and shade. The voicing hand was complex, however, reasonably concrete once the related concepts of voicing and fingering were separated in a way they could be mixed and matched as needed. The skills needed to exploit the potential of the expression hand are less clear and somewhat difficult to master.
It can be difficult to appreciate the full motion required of the expression hand to create the various expressive effects. It is helpful to consider the expression hand as it moves in three dimensional space. Specifically, simultaneous observation from directly in front, behind from the elbow of the expression hand and from the nut. A high-speed video series is currently in the planning stages.

