Madrona Labs has introduced Virta, a voice-controlled software synthesizer for Mac & Windows.
Here are some examples:
Virta combines a low-latency sound analysis module with high-quality synthesis modules in a patchable package, letting you turn voices and instruments into all kinds of sounds.
Virta can also used as a toolbox for effects. Its processing modules, including an input compressor and a pitch shifter with feedback delay, are very open and transparent at low volumes, coloring the sound more when pushed.
Though the audio analyzer is designed to capture the nuances of the human voice, other monophonic instruments produce very musical results, too.
Virta is available now for US $89. A demo version is also available.