Originally developed to do vocal doubling, this plugin is suitable for doubling tracks with vocals, acoustic/electric guitars, bass and just about any other instrument on them. The effect is created by applying small changes to the pitch and timing of the incoming signal. These changes are created by one-dimensional random fractal lines producing pink noise.

source: http://tap-plugins.sourceforge.net/ladspa/doubler.html

Credit: Tom Szilagyi