There are many different scenario's where two or more parts are required to be written on the same stave. These include Keyboard music and Orchestral Scores. Here are some rules for notating divisi/polyphonic parts. This is relevant to the work currently being done on the Denemo Project.
These rules were obtained from Stone's, Music Notation in the 20th Century. W.W Norton & Co.
The occasional crossing of voices is allowed. Where an interval of a third or wider occurs. The note head of the lower part should be aligned slightly to the left of the upper part.
Where an interval of a second occurs. The lower part should align further to the left/right of the upper part. Figure 2 demostrates this.
Accidentals are placed infront of the stems of the lower part. Figure 3 demonstrates this rule.
With dotted notes the dot is placed after the notehead of the upper part's stem. Figure 4 demonstrates this rule
Where three parts on a stave occur each needs to be rythmically simple. Two of the parts must go on one stem. Either the upper or lower part must have the same rhythm. Figures 5, 6, and 7 demonstrate various combinations of this rule. Figure 7 shows the limit of complexity allowed. This means it is usually wiser to have two staves instead of one.
There are two situations where polyphonic staves occur
Accidentals and cancellations need to be written once per bar;
Each line must have its own accidentals and cancellations.
As we saw from the mailing list the most complex that is readable is upto for parts per stave. However, this can cause some problems reading the piece but it should not be discounted. For an example see Trip by Jan Nieuwenhuizen of the Lilypond Team.
Other general rules apply and will be added in due course.
All the examples were produced using GNU Lilypond Typesetter. The examples exaggerate the amount of spacing required when notating them. The Mudela source is also available.
Page produced by Adam Tee