Using tags to produce mensural and modern music from the same source

By using tags, it's possible to use the same music to produce both mensural and modern music. In this snippet, a function menrest is introduced, allowing mensural rests to be pitched as in the original, but with modern rests in the standard staff position. Tags are used to produce different types of bar line at the end of the music, but tags can also be used where other differences are needed: for example using whole measure rests (R1, R\breve etc.) in modern music, but normal rests (r1, r\breve, etc.) in the mensural version. Note that converting mensural music to its modern equivalent is usually referred to as transcription.