added readme

README.md

@@ -0,0 +1,21 @@
+A thing I wrote in January 2007 to write music for the Atari 2600.
+I generated MIDI files and used the pitch bend MIDI controller to 
+adjust each pitch to what the Atari 2600 can output. There was some
+giant document that listed all the frequencies for each distortion
+that the Atari 2600 could emit, and I used that to generate MIDI
+files for each pitch. 15 years later I converted them to ogg so that
+modern browsers could handle them.
+
+What fun!
+
+## Running this thing
+1. [Install PHP](https://www.php.net/downloads.php)
+   - This was written in 2007 so that's like PHP 5.2 or something,
+     but I tested it in 2022 on PHP 8.1.4 and somehow it all still
+     works. It seems impossible but it did.
+2. Run `/path/to/php -S localhost:9999` from this directory
+    - On Windows it'll be `/path/to/php.exe`. Thread safety shouldn't
+      matter so download either version.
+3. Visit http://localhost:9999/ in your browser
+
+![screenshot](./docs/atari-music-editor-window.png)