Surge XT is a virtual instrument plugin previously known as Surge, which (@kurasu) Claes Johanson previously sold as a commercial product through his company, Vember Audio.
As he is too busy with other projects and no longer wanted to put the effort into maintaining Surge across multiple platforms, he decided to give it new life as an open source project.
It was originally released in 2005, and was one of Claes’ first bigger projects. It is reliable and sounds great.
The codebase was migrated from before an unfinished 1.6 release, which improves on the last released 1.5.3 in a number of ways. From this point onward, open source efforts brought Surge to new levels and garnered critical acclaim as one of the best free plugins money cannot buy!
Surge XT currently builds on Windows, macOS, and Linux.