The maker calls user interface design the hardest part of this project, and that shows in how much care went into it. The whole application is written in C++ with the Juce framework, which needs an operating system underneath it, so a Raspberry Pi sits at the heart of the device. Juce has no graphical layout tool, so every screen is laid out in code, which the maker prefers since it suits version control. In my view that is a disciplined way to work, even if it sounds slow.
The hardware itself is a grey 3D-printed casing with exposed screws holding a rectangular faceplate around its perimeter. On the upper left there is a 4x4 grid of mechanical function keys, with an analog thumbstick module in the lower left corner. Seven rotary encoders carry color-coded caps, and a two-octave keyboard of 3D-printed piano-style keys runs across the bottom. The keys are actually mechanical keyboard switches, and the maker found the mechanical keyboard community's design tools made working with them easier. I think repurposing keyboard switches as musical keys is a genuinely clever move for a DIY build.
On the software side, it covers a lot: a multi-track arrangement view, an eight-channel mixer with volume meters, a zoomed-in piano roll, and a built-in four-oscillator synth called 4OSC. The walkthrough includes tapping in a tempo, loading a drum sampler that sequences a sixteen-step pattern, trimming a bass sample via encoder-based beat navigation, and inserting chorus, delay and reverb. Pitch bend is done through the joystick while tweaking saw levels, filter cutoff and ADSR.
One open point: the scrolling animation did not come out as smooth as the maker wanted, and they think switching from the software renderer to open GL might help. Nothing has been open sourced yet either; the maker may release it after polishing the CAD files.
Project by GrievousAngel93. Watch it on their YouTube channel: