Conductor Carolyn Watson introduced her doctoral thesis by arguing that ‘bigger, longer, more involved and complicated performances’ in the nineteenth century ‘necessitated greater conducting involvement through which the role developed’.  Gunther Schuller wrote the following regarding new music:
The problems related to conducting contemporary music are, as might be expected, as varied and unpredictable as contemporary music itself. An unprecedented plethora of compositional schools, techniques, conceptions and philosophies dominate the current scene and it is therefore very difficult to generalize about both the compositional problems themselves and the performance and conducting problems that arise from them. Currently, the art of conducting is undergoing fundamental re-evaluations, and in some instances new compositional approaches have radically changed conducting techniques or, indeed, eliminated them altogether. 
Building on Watson and Schuller’s Musings,  conductor-researcher Hernando Varela stated that conductors’ ‘technique must have a close link with the music it serves’.  Their ‘gesturality’ can be utilized to ‘exceed the operative framework – that is, of communication with the instrumentalists – and becomes a structuring factor of the piece’. 
Watson and Schuller sketch a causal development of the conductor’s role: Western art music becomes more diverse and complicated; therefore, the performance practice of the conductor must adapt. Varela first continues along this causal line by concluding that the technicity of the role must conform to the ‘music it serves’. However, he later remarks that the conductor’s movements now surpass their faciliatory role and become a ‘structuring’ instrument to be utilized by the composer. This is Watson and Schuller’s arguments turned on their heads. At first, the conductor must develop techniques to meet the music. Yet now the music (and composers) develops techniques for the conductors.
This arc, from impromptu to instrumentalized conductor is not linear and certainly not consistent. Not all composers, when deciding to write a conducted piece, decide to actively deploy the conductor. They are happy to have the conductor’s presence continue to be a secondary phenomenon of the music, be that for (economically) traditional, artistical, or pragmatic reasons. As Belgian composer Wim Hendrickx remarked, ‘When I write for a symphony orchestra, I know it is going to be conducted’.  However, as Schuller attests in his Musings, there has been a noticeable trend in an increasingly intricate art music tradition, be that rhythmically, dynamically, visually, or via a multimedia or integrated approach.
Schuller points out that contemporary music is ‘varied and unpredictable’, which makes it ‘very difficult to generalize’.  As such, I plan on attempting no such generalization in this introduction nor in the following pages. Many lines of connection and influence can be drawn through the ranks and multitudes of twentieth and twenty-first century Western art music. However, I would like to draw one line here that perhaps can illustrate the developments described by the above-cited conductors and researchers, one from Charles Ives’ (1874-1954) Symphony No. 4(1910-1916), to Karlheinz Stockhausen’s (1928-2007) Gruppen (1955-57), to Mark Applebaum‘s (1967- ) Tlön (1995).
 Carolyn Watson, ‘Gesture as Communication: The Art of Carlos Kleiber’ (Doctoral Thesis, University of Sydney, 2012), 2.
 Carl Bamberger, ed., The Conductor’s Art, Columbia University Press Morningside ed (New York: Columbia University Press, 1989), 189.
 Gunther Schuller, Musings: The Musical Worlds of Gunther Schuller (New York: Oxford University Press, 1989).
 Hernando Varela, ‘Adecuación, Expansión y Ruptura. La Técnica Gestual de La Dirección Musical En Composiciones de Los Siglos XX y XXI’, Revista 4’33" Año IX, no. 19 (December 2020): 33–53.
 Wim Henderickx, interview by Thomas R. Moore, 22 January 2020.
 Bamberger, The Conductor’s Art.