While writing my prior post on the posting of all of Mozart’s manuscripts online, I got to thinking about other forms of writing than plain text, of which music is one example.
Mozart’s manucripts are in a musical notation. According to the cited Wikipedia article, musical notations have existed for thousands of years, and the current “Western” notation dates back almost a thousand years.
It’s a good thing that music notation has been around so long. Imagine if it were a recent invention, and was available only in a proprietary format such as that used by Microsoft Office? Or imagine our grief if Mozart’s Marriage of Figaro had been published using Salzburg Office, version 1786? And let’s not think about the DRM measures that would be put in place to lock down that wonderful music these days …
While most folks in the open-source arena think mainly about the code, it’s also important that the data be open. For example, suppose Mozart had been subject to the whims of a colonial upstart, Micro Doodle software, and had written his music using the proprietary music font, TrueMusic Macaroni. See Yankee Doodle, and Yankee Doodle. He might even have written some songs about it:
Micro Doodle went to town,
It stuck a new fork in its code,
And called it macaroni. 
Micro Doodle, keep it up,
Micro Doodle dandy;
Mind the music and the step,
And with the cash be handy!
1. This is common practice, particularly in large software projects. It’s called “spaghetti code.”