Wind Chimes, Aeolian Harps, and Machines That Play Themselves
Short answer: Music that plays itself is much older than computers. A wind chime, a harp played by the wind and an 18th-century dice game all rest on one idea. A person decides which sounds are allowed, and chance decides the order. My app is that idea with drifting shapes in place of wind.
Wind chimes: choose the notes, let the wind choose the order
Wind chimes are very old. Wikipedia says "Ancient Roman wind chimes, usually made of bronze, were called tintinnabula". It also mentions wind bells on the corners of pagodas in India and later China, and Japanese glass chimes called fūrin.
The same page says chimes "have been considered an example of chance-based music". Nobody plays them. The wind does.
What interested me most was the tuning. Wikipedia again: "Most chimes employ pentatonic or tetratonic scales". A five-note scale has no two notes that clash badly. So whatever order the wind picks, it sounds fine.
That is the whole design. The maker never controls the tune. They control what the tune is allowed to contain.
I ended up in the same place. Ocean and Forest are both tuned to five-note scales. Any two shapes can meet at any moment and I can't know which, so I made sure no meeting can sound sour. Space uses only the notes of one open chord, so no meeting can clash there either. Its first, stranger scale is in whole tones have no home.
The aeolian harp: sound that swells and never strikes
An aeolian harp is a wooden box with strings stretched across it. You put it where the wind blows and the wind plays it. It's named after Aeolus, the Greek god of wind. Wikipedia says the scholar Athanasius Kircher described it in 1650 and that it became a popular household object in the Romantic era. Coleridge wrote a poem called "The Eolian Harp".
The physics surprised me. According to Wikipedia, the wind makes the strings produce only overtones and never their basic note. So the harp sings in high, ghostly tones that rise and fall with the wind. The article calls them "crescendos and decrescendos of harmonic frequencies".
That makes it the opposite of a chime. A chime is struck, so it gives you separate events. A harp has no strikes at all. Its sounds grow and fade.
My app has both kinds. Some sounds fade in while two shapes overlap and fade out when they part, like the harp. Others fire once at the moment of touching, like a chime. I only noticed afterwards that I had rebuilt both instruments.
The dice game: chance inside a frame
In 18th-century Europe there was a fashion for composing with dice. Wikipedia describes it: "The dice rolls randomly selected small sections of music, which would be patched together to create a musical piece." The earliest example it gives is by Johann Kirnberger, from 1757. A well-known version was published in 1792 under Mozart's name, though Wikipedia notes the attribution "has not been authenticated".
Here the composer writes the fragments and the table, so that every possible roll gives a decent dance. The composing has moved from the piece to the system that makes pieces.
What the three share
- A person fixes the material: the notes, the strings, the fragments.
- Something outside their control picks the order and the timing.
- The skill is in making every possible outcome acceptable.
The third point is where most of my time goes. Making one nice sound is the easy part. The work is making sure no combination of them is ugly.
What a computer adds
You can't carry wind in your pocket. In my app the wind is the movement of shapes across the screen, and you can push them around yourself.
The rules can also be richer than a chime allows. Mine include a slow pulse that keeps things loosely in time, and limits on how many sounds can play at once. Those are in the drone is the clock and voice limits.
Sources
Try it: Open Ambient Sound Online and drag a few shapes across each other in Ocean. It's free. You are the wind.
Open Ocean, free