EP by Aphex Twin, 1999.

1. Windowlicker
2. (Equation)
3. Nannou

I make exception to my noding standards here. I will not node this where it goes, because no one in hell will be able to find it from under the appropriate node title if I put it there. Plus, even TeX almost chokes on this...

The second track on the EP is pretty interesting one. Most often it's referred to as "equation" or "strange formula" or something like that.

The title in TeX notation (the CD and the websites use pretty simplified font, I hope this is correct this time):

$$\Delta M^{-1}_{1} = -\alpha\sum^{N}_{n=1}D_{i}[n] \left[ \sum_{j\in{}C\{i\}} F_{ij}[n-1]+F\hbox{ext}_{i}[n^{-1}] \right]$$

Put that to your title search and smoke it! =)

The piece is, as the title suggests, mathematical in nature.

To fully enjoy the music, you need a spectrum analyzer that can draw a continuous spectrogram of the sound. (eXtace is pretty good, if you're on UNIX.) For best results, use analyzer that can display sound on logarithmic scale. (eXtace isn't good in this respect because it only uses linear scale. I found one tool (snd) that uses logarithmic scale somewhat better but not quite right.)

This is the first CD I've needed to buy due to technical quality of stuff shared in web, this time it has nothing to do with not being able to find a file that sounds good! =)

While the most of the track has synthetic sounds, there's something else in it not entirely audible. Look closely to the spectrum analyzer. It will look... strange. It will have pictures in it. There are several pictures and patterns visible in the song's spectrogram, some are reportedly not well visible if you use a crappy encoder. (The pictures in the .ogg I found before I got the CD were recognizable, if at times mangled...)

I think it's one of the first cases for me when I need FLAC... I suppose this piece is also very good for comparing the relative quality of some lossy audio encodins.

One thing is sure: I will never look at (or listen to) the music the same way! And maybe this will change the way how fundamentalist Christians analyze music. =) (See also backwards masking)

For the terminally lazy, here are pictures of the last "big ugly face" in the end of the piece:

http://www.aphextwin.nu/learn/99906995499023.shtml
http://www.joyrex.com/photos/gallery/equation_face.jpg
http://www.visualizationsoftware.com/gram/example15.html

(The first is distorted due to use of linear frequency axis... Latter two use logarithmic axis.)

(Carthag informs me that this is actually no one other than Richard D. James himself!)