Mother is a library for Processing for facilitating the creation of AV projects. During NIME 2014, I met Ilias Bergstrom, one of its creators.
From http://www.onar3d.com/mother/ :
“The limited aesthetic flexibility permitted by existing tools however has meant that artists striving to differentiate their work have most often been the inventors and creators of the tools they use. To address this obstacle, we have developed a set of tools, that make use of and extend the popular Processing open-source multimedia programming environment.”