Explain please? It turns your PowerBook's speakers into mics ?!?!
hunh?

I guess, it takes input from microphone and feeds it back into the speakers/headsets. This way, if you have your headsets on and there's music playing, you'll still be able to hear people talking to you. I'm just guessing from description here, though.

That's right. It's based on Max/MSP. It takes the mic input from the built in mic or other mic if I have one attached attached and mixes it with the music from iTunes so I'm not completely isolated. - Joi Ito

Joi, this sounds very cool, and reminds me of something I used to play
with quite a bit, binaural sound.

You probably already know about this, but if you don't, it seems like something you'd like, a method of sound recording using a set of two microphones that are 'ear distance' apart and separated by either a 'dummy head' or your own head.

There are special microphones that are designed for this, but I used to use a pair of Audio-Technica open-back dynamic headphones - they worked very well. The result is you get a unique stereo recording that when played back through headphones (this is mandatory - the effect wont work with speakers) reproduces an uncanny sense of space, reproducing the sound field so realisticly that if you close your eyes, you can almost feel yourself there.

It's not as easy to set this up with computers as it was with my old stereo Walkman pro that I used to do binaural with, but if you want an interesting recording of an auditory event, its often worth the effort.

Chris Beaumont

 ... OK, so I was wondering... if you're listening to music, and someone comes into the room, sits down, and squeaks their chair, does it come through to your headphones?

Hi

this is michael breidenbruecker, i created the original mic4joi app. I dropped the whole idea during the time when doing last.fm but decided to do some new stuff with mic4joi. I added some features which bend the real sound, so your soundspace and realspace getting mixed up. Try it, you can find the application here.
Chris: I used the the application in conjunction with binaural microphones. works very well.