Audio Chaos Soundscape Generator was a free program that would let you create on your computer background / ambience music (soundscapes), using various audio samples.

With the right number, and combination of sounds you could create some interesting soundscape environments or randomly generated music, such as rain with thunders and animal sounds, etc.

With some light rain, a few bird noises, some wind and sound effects, you could create a surprisingly interesting and ever-changing soundscape.

Unfortunately the program is not developed anymore, but you can get White Noise instead. White Noise provides ambient sounds.

• Download White Noise