This is an editor for the ABC music notation, utilizing abcjs library.
ABC notation is the "Markdown for music". Learn more at https://abcnotation.com/.
Available at Visual Studio Marketplace or through the Extensions panel in VS Code.
The extension displays the music sheet based on the Abc notation in the current editor. Clicking the note on the displayed sheet will select it in the editor.
And a bit more elaborate:
The only action available currently is "abcjs-vscode: Show Preview". Press Ctrl+Shift+P and type "abcjs" to access it.
The abcjs library is currently loaded from CDN and not packaged with the extension.
There are currently no settings for the extension. It works on blank new files and existing .abc files.
The line-endings in the file need to be set to LF instead of CRLF (on Windows). Then the offsets will match between the sheet and the abc code.