Once upon a time while tripping across the 'net I stumbled upon a piece of software called Resonance. The web site is cryptic:

resonance includes a mathematically-precise binaural tone generator, capable of producing fifteen hundred unique binaural frequencies.

What is a binaural tone? Why would I want to listen to one? I downloaded it to find out.

The interface is equally mysterious, but fortunately it has some presets which immerse you into audio soundscape that defies clear description. Those binaural tones were pulsating, interacting stereo waves that gave me a tingly feeling, the kind of feeling that you get when you're learning something profound. Maybe some people would call it a spiritual feeling.

If you look up binaural tones, the great wiki has some descriptions of odd and perhaps unbelievable effects they can have on your body and brain. I don't know if I believe a word of it. But I do believe there is something odd happening when I listed to Resonance.

The author does because he created the program to help him concentrate:

I personally use it when I am programming or writing, basically whenever I need a lot of concentration. Others use it for relaxation, sleep aid, meditation, yoga, background noise...etc. [via email]

He also pointed out that for best effect you should use headphones with no other sound or music playing. Even though, Resonance does include a variety of natural sounds effects from the Earth Recordings library -- which accounts for the large size.

This is definitely an odd program, but I have a feeling that it would be a great candidate for conversion to the iPhone, where I think it could gain a cult following.

Bottom line: if you're interested in audio phenomena or unusual interface design, check it out. Resonance.