This article presents Jacdac-for-Max: a cross-platform, open-source set of node.js scripts and custom Cycling '74 Max objects which enable the use of Jacdac, an open, modular plug-and-play hardware prototyping platform, with Max visual programming language frequently used for audio-visual applications. We discuss the design and implementation of Jacdac-for-Max, and explore a number of example applications. Through this we show how Jacdac-for-Max can be used to rapidly prototype digital musical interfaces based on a range of input devices. Additionally, we discuss these qualities within the context of established principles for designing musical hardware, and the emerging concepts of long-tail hardware and frugal innovation. We believe that through Jacdac-for-Max, Jacdac provides a compelling approach to prototyping musical interfaces while supporting the evolution beyond a prototype with more robust and scalable solutions.