analog_cd_music

Out of the Blue

I read this article today. The guy's idea was a good one, an electronic instrument embedded within a cd case, but he didn't notice one blindingly obvious thing about cds that he could exploit to really good effect. Obviously in my godly awesomeness I noticed the exploit right away, hence this post, but if you don't have a clue what I am getting at then I will explain further.

CDs are Vitreous

If you know a thing or two about compact disk technology you will know that a cd is basically a thin aluminum film sandwiched between two layers of plastic. The aluminum is etched with a laser in the cd drive, allowing data to be stored and read back off. That layer of aluminum is very thin, almost transparent. A fully written to cd is even more see-through because the laser etches tiny pits, thinning the metal. So if you try and look through part of a cd where no label is printed you will be able to see what is on the other side. That property is what my idea exploits.

A Digital Analog Music Box

Those old music boxes that you cranked to play operate by the same principle that my cd based idea does. In a music box different pegs on a big drum hit little rods that play different tones. If you replace the drum with a cd, simulate the pegs with different printed patterns on the disc, and emulate the rods by using a single light sensor you can have music play off of the label of a cd. As the disc spins ambient light falls through the label on the CD and onto a light sensor. A circuit turns the changing light levels into a changing tone, output through a speaker. The disc label could use dithering to change the amount of light that gets through.

For Those Without a Picture

If you still don't get it, then let me explain it in a different way. You buy a cd. It comes in a normal cd case. In that case is a circuit board instead of the regular label. There is a pattern printed in a spiral on the cd. You spin the disc in the case. You hear a sample of the the music that is on the disc play from the case. ANALOG MAGIC!