This paper introduces the OWL stage effects pedal and aims to present the device within the context of Human Computer Interaction (HCI) research. The OWL is a dedicated, programmable audio device designed to provide an alternative to the use of laptop computers for bespoke audio processing on stage for music performance. By creating a software framework that allows the user to program their own code for the hardware in C++, the OWL project makes it possible to use homemade audio processing on stage without the need for a laptop running a computer music environment such as Pure Data or Supercollider. Moving away from the general-purpose computer to a dedicated audio device means that some of the potential problems and technical complexity of performing with a laptop computer onstage can be avoided, allowing the user to focus more of their attention on the musical performance. Within the format of a traditional guitar ’stomp box’, the OWL aims to integrate seamlessly into a guitarist’s existing pedal board setup, and in this way presents as an example of a ubiquitous and tangible computing device -a programmable computer designed to fit into an existing mode of musical performance whilst being transparent in use.