ModulysCS is built around ModulysVst which is a giant step-sequencer/phrase generator in Vst-plugin format. ModulysCS is a portable app for Windows (15MB zip-file) and includes a Csound CSD-editor.
You can create your own presets and instruments. It uses Csound 6.15.0 api for communication and sound generation.
It’s totally free without restrictions.
For more info see