stk: STK (Synthesis ToolKit) stk: stk: The Synthesis ToolKit in C++ (STK) is a set of open source audio stk: signal processing and algorithmic synthesis classes written in stk: the C++ programming language. STK was designed to facilitate rapid stk: development of music synthesis and audio processing software, with stk: an emphasis on cross-platform functionality, realtime control, ease stk: of use, and educational example code. stk: stk: stk: