See it in action at https://tbaldw.in/copland.
This little music-making experiment encourages the user to create patterns by clicking boxes which represent different pre-determined pitches. The piano sounds of the grid on the left move 16x faster than the string sounds of the grid on the right. The string harmonies were selected to sound more-or-less consonant with the pitch palette of the piano grid. Clicking the colored box results in a shift to a new pitch palette for both grids.
Pressing the space-bar or the return key pause and play the loop. The backspace clears the grid. And pressing the letter 'e' causes the grid to start 'evolving' - adding and removing pitches strategically. The idea here is that the user can leave the application running in the background, enjoying the variety of patterns generated by the application's evolution algorithm.
You can leave Copland running in the background but it generally performs better when it has a window all to itself.
Users may also save their creations by pressing the letter 's'. This will pull up a URL which should load in the creation at the start.
The name "Copland" comes from the American composer Aaron Copland, whose Pulitzer prize-winning work, "Appalachian Spring" inspired the sound palette.
There are still a few issues here and there. And reporting bugs is much appreciated!