One of my favorite things in emacs. When confronted with an arcane, custom "language" developed 30 years ago because of some immediate need without serious care taken. You can create a custom mode that gives you syntax highlighting, indentation support and other things fairly quickly. And it beats the built-in "editors" present in a lot of tools, especially those that don't let you directly edit the text file but insist on making you click through wizards and dropdown menus.
Once you've got the basics written, you can start to work. Then add imenu support, and you have file browsing. Then add your language to exuberant ctags - which has a line-based regexp mode that you can pretty much reuse your imenu regexps for - and get it to generate emacs-compatible tags files, and you've got basic cross-file symbol navigation.
(The quality of ctags-based symbol browsing can be hit or miss - for languages like Java or C++, where many mechanisms require symbols to be identically-named, it's not that great. But not-that-great is still a lot more convenient than nothing.)
Do you mean this?
Though octave was originally a music term too.
Sorry, it's a pet peeve of mine that people keep thinking that GNU Octave has something to do with music.