This article reflects on how personal digital musical instruments evolve and presents an augmented violin developed and performed by the author in improvised performance as an example. Informed by the materialism of Gilles Deleuze and Felix Guattari, an image of ‘flows of inhomogeneous matter’ provokes reflection on a mode of production common to artisanal craftmanship and digital lutherie alike, namely the pre-reflective skilfulness negotiating the singularities of inhomogeneous matter with the demands of the production – a process which itself may be thought of as im-pro-visation (‘un-fore-seen’). According to Gilbert Simondon, all technical objects develop in this way: functional interdependency emerges when abstractly ideated elements begin to enter into unanticipated synergistic relationships, suggesting a material logic dependent on unforeseen potentialities. The historical development of the acoustic violin exemplifies such an evolution, with, like all technical objects, additional latent potential. Digital artists can work like artisanal craftsmen in tinkering with technical elements, teasing out their synergies through abductive, trial-and-error experimentation. In the context of developing digital musical instruments, model-free design of real-time digital signal processing symmetrising action and perception yields highly refined results. Like musical improvisation – constrained by time – improvised development of these instruments turns the material obstacles into their very means of realisation.