regex101 : Free PCRE-based regular expression debugger with real time explanation, error detection and highlighting.
ixi software : ixi audio is an experimental project concerned with the creation of digital musical instruments and environments for generative music.
sfxr : A tool to quickly generate 8bit/16 bit-soud effects!
librosa : librosa is a python package for music and audio analysis. It provides the building blocks necessary to create music information retrieval systems.
VST Plugins Free - Virtual instruments and effects
