Ansible - Radically simple configuration-management, application deployment, task-execution, and multi-node orchestration engine
Serum - VST for FL Studio, Ableton Live, and many other VST supported DAWs. Heavily utilized in EDM.
Jenkins - Jenkins is an open-source continuous integration server with 300+ plugins to support all kinds of software development
Surge XT - Open-source subtractive-hybrid synthesizer formerly sold commercially as Vember Audio Surge.
Puppet Enterprise - Get started with Puppet Enterprise, or upgrade or expand.
Omnisphere - Piano, pad and synth VST for DAW's.