2MGT/Metamusic Generative Tools has released EVOX, an Experimental Soundscape Synthesizer. It's available as a free/donation standalone application for Windows.
Here's what they say:
This is not a sampler or a player, EVOX is an experimental soundscape synthesizer that employs two separate and programmable layers each with extensive FX and Modulation Matrix modules which provide the user with maximum control over unique sound creation.
With the built-in 16 track Crossfade Pattern Sequencer, long evolving ambient/drone sounds can be created and cross-faded with other sounds to create dense tapestries of sound.
As an experimental synthesizer it radically departs from standard instruments and is meant to be used as a laboratory for the exploration of new sonic and timbral creations that would be difficult to achieve any other way. It is ideal for ambient soundscapes or virtually any type of experimental genres.
As the user becomes more familiar with its various controls and parameters the possibilities for sounds that are surprising and unexpected are greatly enhanced.