Sointu
Modular software synth for 4k intros that grew out of 4klang and was rebuilt for modern tooling and more platforms.
Finnish coder Veikko Sariola (pestis) started it around 2020 as a fork of 4klang, whose code had become hard to extend. The core idea is unchanged — a stack-based synth whose music is exported as compact code — but the surrounding tools are written in Go, with a tracker of its own alongside the VST plugin.
Where 4klang was tied to 32-bit x86, Sointu can also generate code for 64-bit systems and WebAssembly, so the same tune can play in a Windows intro and in a browser. The name is Finnish for roughly "chord" or "sound", which makes the family resemblance about as obvious as it gets.