String quartet template with separate parts

The String quartet template snippet produces a nice string quartet, but what if you needed to print parts? This new template demonstrates how to use the \tag feature to easily split a piece into individual parts.

You need to split this template into separate files; the filenames are contained in comments at the beginning of each file. piece.ly contains all the music definitions. The other files – score.ly, vn1.ly, vn2.ly, vla.ly, and vlc.ly – produce the appropriate part.

Do not forget to remove specified comments when using separate files!