2MGT/Metamusic Generative Tools has released EVOX Calypso, an experimental soundscape synthesizer. It's available as a free/donation standalone application for Windows.
EVOX Calypso (which originated from the EVOX tool) is a creative laboratory for creating cinematic ambient soundscapes, sound structures, atmospheric and ethereal textures, deep drones, as well as more traditional synthesizer sounds that can be layered, to create variety of spatial sounds.
Playing EVOX Calypso is not like playing a conventional synthesizer, it does not have a keyboard and MIDI GUI like conventional synthesizers. Sound manipulation is carried out by built-in modulators and sequencers.
EVOX Calypso also has an 8-track sequencer with up to 64 steps for each track. Each track is essentially a separate synthesizer that can be recorded and played back in sync with the other tracks. Mini compositions can be made by merging these tracks together.
Price: Free/Donate. No installation is necessary, and it works on Windows XP and Windows 10 (32/64-bit) (EVOX Calypso is 32-bit).