librosa : librosa is a python package for music and audio analysis. It provides the building blocks necessary to create music information retrieval systems.
Opentape : Opentape is a free, open-source package that lets you make and host your own mixtapes on the web.
Upload songs (via web or FTP), reorder, rename, cust...
ixi software : ixi audio is an experimental project concerned with the creation of digital musical instruments and environments for generative music.
regex101 : Free PCRE-based regular expression debugger with real time explanation, error detection and highlighting.
VST Plugins Free - Virtual instruments and effects