| Recent attempts to extend organology to add useful classifications of electrophones and music controllers have rightly focussed on music performance gestures . The naive approach of classification by gestural types (strum, pluck, hit, slap etc..) fails because gestures say more about musicians and their music than their instruments. The routine development in institutions of "extended" techniques and the drive for uniqueness and theatricality in popular music practice results in each instrument being associated with an increasing number of different performance gestures defeating useful, differentiating classifications. Also, Hendrix's enkindling of the guitar guitar, or Townsend's windmill strum are gestures associated with a time, an individual, and a repurposed ritual but such gestures could be used on any instrument. The british sport of piano bashing where the winning team is the fastest to destroy and put an entire piano through a letterbox reminds us of the wide range of expected and unexpected gestures that may be associated with musical instruments.
A more fruitful approach is to classify by structural attributes looking from the controller out toward the performer. The example I will focus on is fingerboard controllers and instruments. This family includes the guitar and cello but not the harp, dividing traditional chordophones in a way that makes sense with common performance practice. All these instruments can be strummed by virtue of their strings but the hammer-on and pull-off are not available on the harp. More interestingly this classification organizes the early electrophones and early and recent controllers. The Ondes Martenot, Hellertion, Trautonium, and Theremin cello, synthesizer ribbon controller, Continuum fingerboard and Guitar Hero are members of the fingerboard instruments but the Theremin and organ are not.
Like all effective classification systems this one yields some annoying but interesting edge cases like the koto and iPhone. The koto player doesn't interact with a fingerboard directly but the pillars on the sound board, that divide each string are essential to the pitch bending affordances of the instrument. The iPhone has both proximity sensing (a la Theremin) and a surface for finger interaction whereas most of the other fingerboard instruments have a chord, strip or switch between the player and the fingerboard.
An interesting feature of fingerboard controllers is that they can be differentiated from each other by structural features integrated to discretize gestures - usually those that involve pitch. These fiducials may be visual (slide guitar, iPhone), mechanical (frets), statically haptic (dimples of the Ondes Martenot), or actively haptic (lamella of the Trautonium).
The fingerboard classification allows us to frame David Wessel's Slabs and my own recent controllers as members of a family of related controllers with a long tradition rather than as "unique inventions" whose newness has to be confronted. On the Slabs the fiducials are a rectangular grid of slits with the interaction pads tiled between them in two dimensions,. My "Big Guitar" can be seen as a hybrid koto, fretless bass guitar and Hellertion. My Tablo fabric drape controller shares features of the Hellertion and Theremin cello with a distinguishing annular fingerboard. The 12-stringless cello developed with Frances Marie Uitti has features of ribbon controllers but with position/pressure sensing strips on both sides of the fingerboard and a structurally independent array of rods for two-bow interactions.
This framing encourages the appoach of design space exploration for future controllers instead of the common (romantic) idea of a quest for "invention" of a disruptive breakthrough new controller.
Also, this framing suggests an atypical answer to the question of which field new musical controller design and development belongs in, i.e. the plastic arts. One definition (wikipedia) of the plastic arts is that they "involve the use of materials that can be molded or modulated in some way often in three dimensions." This new lutherie stands alongside architecture, textile arts and sculpture involving issues of both concrete forms/structures and engagement of multimodal interactions.