This is just plain cool.
In fact, this is the first iPod app that I've paid for (a big, bad $3.99).
Brian Eno has co-written (along wth Peter Shilvers) an iPhone/iPod Touch application called, "Bloom" -- "Part instrument, part composition, part artwork."
"Bloom" has two modes: "Listen" and "Create" (essentially, "Auto" and "Manual"). "Listen" mode produces spontaneously generated ambient music. "Create" turns your phone/pod into an ambient musical instrument.
Here's how it works: First, there's a low volume background drone. Whenever you touch the screen, it plays a note -- the top of the screen produces high notes, and the bottom of the screen produces low notes. Where you touch blooms into one of the circles you see in the photo. As the note fades out, the circle gets larger and fades out. Then, a few seconds later, it repeats the note (and redraws the circle). The note (and the circle) repeat at regular intervals, growing gradually softer over the course of a minute or two. Touch two or three fingers simultaneously, and you make a chord.
So if you play a sequence of notes and chords, the sequence repeats a cycle (and a pattern of circles on the screen). As you add new notes and chords to the sequence, the overall image and sound shifts over time as the earlier sequences fade out. The music is very akin to Eno's Ambient Music -- seemingly meterless, but not without organization, shifting textures.
The settings include a volume control, a sliding scale to increase or decrease the frequency with which notes repeat, a "Shake to clear" On/Off switch (just what it sounds like -- if you get tired of a sequence, shake the phone/pod like an Etch-A-Sketch to clear the screen and start over), a "Clear" button, a "Freeze" button (stops notes from fading out and freezes the existing pattern) and a "Listen" button to switch to the random note generation mode. There are settings for the color schemes of the visuals (default to "Shuffle"), plus a switch that says if the app stays idle for any significant time, it will start to repeat a pattern that you entered earlier.
It's an utterly fascinating toy. I spent most of my 45-minute ride on the F-Market playing with it this morning, and I had trouble putting it down when I got to work.
I also notice that the Apple Blog mentions that there is a free phone/pod app version of Eno's classic "Oblique Strategies" (a set of oracle cards that Eno created in the 1970s to assist him the creative process), and a quick check at the iTunes store confirms that there is, indeed, a free "Oblique Strategies" app. The oracle cards are chiefly intended as suggestions on how to get past creative hurdles. When you get writer's block, pick a card at random from the deck and follow the instructions: "Look closely at the most embarrassing details and amplify them" or "Turn it upside down" or "Cascades" or "Bridges (burn)". The phrases on the cards are intentionally open to interpretation, and they are not intended to give you instructions so much as ideas.
So I might have to try the "Oblique Strategies" app later as well.