wxWidgets - wxWidgets: Cross-Platform GUI Library
Go Button - Go Button is a mobile audio app designed to provide professional playback of music and sound effects for live shows. It provides a creative, self-contained show control system that runs on your iPad, iPhone, or iPod touch.
Electron - Build cross platform desktop apps with web technologies
AudioBus - With Audiobus, the revolutionary new inter-app audio routing system, you can connect your...
GTK - GTK+ is a multi-platform toolkit for creating graphical user interfaces.
Setlists - Setlists app enables users to prompt lyrics of the desired song by synchronizing the data with all the other musicians on stage, and they can change the order of tracks in their song catalog.