In recent years, the Pupil Accommodative Response (PAR) has emerged as a promising communication strategy in Human-Computer Interaction (HCI) and augmentative and alternative communication devices. In fact, the PAR is a repetitive, high-magnitude and low-noise innate response. Previous studies exploited the far-to-near focus switch that induces the PAR to extract a binary output. This preliminary study has introduced the potential for detecting intermediate levels of response, with the aim of extracting a non-binary output from pupil size variations induced by shifts in focus between multiple targets. In the current context, this strategy was applied to a music machine, where the pupil size is continuously monitored and converted into musical notes resulting in a jazz melody. This article aims to present the preliminary results of the developed system and to explore the challenges and limitations associated with this type of application. In addition to entertainment, usefulness of this approach includes enhancing user awareness about the physiological function and the voluntary control of pupil size. In perspective, the approach adopted for the music machine may be exploited in pupil-based HCIs to achieve higher information transfer rates.