Idea: Simple aid for the blind

I need to google a bit to see if this exists, but here's the idea...

I've got a friend who is a great musician, who also happens to be blind. It got me to thinking that blind people tend to have very good ears. Could they pick out different pitches in a chord well enough to use it for sight?

So imagine this device: one or two digital cameras (nothing too flash, the resolution you can manage would be pretty low I think with this device). Process the video stream into audio: any pixel can placed left<->right using a standard stereo pan position, and up<->down can probably be accomplished with pitch. Hmm, could you have enough different pitches to do this without it turning into a complete wash? If you used to cameras, could depth be done using a combination of audio level and some kind of echo effect? There is standard stuff people do in audio to achieve depth, anyway, so do that.

So we actually have two dimensions unaccounted for. up<->down for which I'm proposing pitch (would that just be awful?), and colour, which you might just leave out.

Is someone already doing this? Is the idea just completely stupid? It strikes me that you could probably get a couple of simple digital cameras for a couple of hundred dollars each (webcam level cameras), and a wearable computer for somewhere under $2000 (not sure about that, need to go hunting online). Steve Mann's stuff is the place to look, actually, he does wearables, and is big into video input. The only other thing you need is a $10 pair of headphones :-)

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lol, 1 minute after posting I found this:

The Optophone
What is an optophone

This device was invented over 100 years ago :-)

However, it doesn't appear to have been commercialised successfully. It might do some good to put together a minimum cost recipe to allow people to cobble one together from cheaply obtained off-the-shelf components.

Here's a java applet that does it but uses time instead of stereo pan to give left->right; it sweeps once every second or so. Why why why do they not use stero pan????