LilyPond 学习手册: 5.6.3 Real music example

### 5.6.3 Real music example

We end this section on Tweaks by showing the steps to be taken to deal with a tricky example which needs several tweaks to produce the desired output. The example has been deliberately chosen to illustrate the use of the Notation Reference to resolve unusual problems with notation. It is not representative of the more usual engraving process, so please do not let these difficulties put you off! Fortunately, difficulties like these are not very common!

The example is from Chopin’s Première Ballade, Op. 23, bars 6 to 9, the transition from the opening Lento to Moderato. Here, first, is what we want the output to look like, but to avoid over-complicating the example too much we have left out the dynamics, fingering and pedalling.

We note first that the right hand part in the third bar requires four voices. These are the five beamed eighth notes, the tied C, the half-note D which is merged with the eighth note D, and the dotted quarter note F-sharp, which is also merged with the eighth note at the same pitch. Everything else is in a single voice, so the easiest way is to introduce these extra three voices temporarily at the time they are needed. If you have forgotten how to do this, look at I’m hearing Voices and Explicitly instantiating voices. Here we choose to use explicitly instantiated voices for the polyphonic passage, as LilyPond is better able to avoid collisions if all voices are instantiated explicitly in this way.

So let us begin by entering the notes as two variables, setting up the staff structure in a score block, and seeing what LilyPond produces by default:

>     rhMusic = \relative {
>       \new Voice {
>         r2 c''4. g8 |
>         bes1~ |
>         \time 6/4
>         bes2. r8
>         % Start polyphonic section of four voices
>         <<
>           { c,8 d fis bes a }  % continuation of main voice
>           \new Voice {
>             \voiceTwo
>             c,8~ 2
>           }
>           \new Voice {
>             \voiceThree
>             s8 d2
>           }
>           \new Voice {
>             \voiceFour
>             s4 fis4.
>           }
>         >> |
>         g2.  % continuation of main voice
>       }
>     }

>     lhMusic = \relative {
>       r2 <c' g ees>2 |
>       <d g, d>1 |
>       r2. d,,4 r4 r |
>       r4
>     }

>     \score {
>       \new PianoStaff <<
>         \new Staff = "RH"  <<
>           \key g \minor
>           \rhMusic
>         >>
>         \new Staff = "LH" <<
>           \key g \minor
>           \clef "bass"
>           \lhMusic
>         >>
>       >>
>     }

All the notes are right, but the appearance is far from satisfactory. The tie collides with the change in time signature, some notes are not merged together, and several notation elements are missing. Let’s first deal with the easier things. We can easily add the left hand slur and the right hand phrasing slur, since these were all covered in the Tutorial. Doing this gives:

>     rhMusic = \relative {
>       \new Voice {
>         r2 c''4.\( g8 |
>         bes1~ |
>         \time 6/4
>         bes2. r8
>         % Start polyphonic section of four voices
>         <<
>           { c,8 d fis bes a }  % continuation of main voice
>           \new Voice {
>             \voiceTwo
>             c,8~ 2
>           }
>           \new Voice {
>             \voiceThree
>             s8 d2
>           }
>           \new Voice {
>             \voiceFour
>             s4 fis4.
>           }
>         >> |
>         g2.\)  % continuation of main voice
>       }
>     }

>     lhMusic = \relative {
>       r2 <c' g ees>2( |
>       <d g, d>1) |
>       r2. d,,4 r4 r |
>       r4
>     }

>     \score {
>       \new PianoStaff <<
>         \new Staff = "RH"  <<
>           \key g \minor
>           \rhMusic
>         >>
>         \new Staff = "LH" <<
>           \key g \minor
>           \clef "bass"
>           \lhMusic
>         >>
>       >>
>     }

The first bar is now correct. The second bar contains an arpeggio and is terminated by a double bar line. How do we do these, as they have not been mentioned in this Learning Manual? This is where we need to turn to the Notation Reference. Looking up ‘arpeggio’ and ‘bar line’ in the index quickly shows us that an arpeggio is produced by appending `\arpeggio` to a chord, and a double bar line is produced by the `\bar "||"` command. That’s easily done. We next need to correct the collision of the tie with the time signature. This is best done by moving the tie upwards. Moving objects was covered earlier in Moving objects, which says that objects positioned relative to the staff can be moved vertically by overriding their `staff-position` property, which is specified in half staff spaces relative to the center line of the staff. So the following override placed just before the first tied note would move the tie up to 3.5 half staff spaces above the center line:

`\once \override Tie.staff-position = #3.5`

This completes bar two, giving:

>     rhMusic = \relative {
>       \new Voice {
>         r2 c''4.\( g8 |
>         \once \override Tie.staff-position = #3.5
>         bes1~ |
>         \bar "||"
>         \time 6/4
>         bes2. r8
>         % Start polyphonic section of four voices
>         <<
>           { c,8 d fis bes a }  % continuation of main voice
>           \new Voice {
>             \voiceTwo
>             c,8~ 2
>           }
>           \new Voice {
>             \voiceThree
>             s8 d2
>           }
>           \new Voice {
>             \voiceFour
>             s4 fis4.
>           }
>         >> |
>         g2.\)  % continuation of main voice
>       }
>     }

>     lhMusic = \relative {
>       r2 <c' g ees>2( |
>       <d g, d>1)\arpeggio |
>       r2. d,,4 r4 r |
>       r4
>     }

>     \score {
>       \new PianoStaff <<
>         \new Staff = "RH"  <<
>           \key g \minor
>           \rhMusic
>         >>
>         \new Staff = "LH" <<
>           \key g \minor
>           \clef "bass"
>           \lhMusic
>         >>
>       >>
>     }

On to bar three and the start of the Moderato section. The tutorial showed how to add a tempo indication with the `\tempo` command, so adding “Moderato” is easy. But how do we merge notes in different voices together? This is where we need to turn again to the Notation Reference for help. A search for “merge” in the Notation Reference index quickly leads us to the commands for merging differently headed and differently dotted notes in Collision resolution. In our example we need to merge both types of note for the duration of the polyphonic section in bar 3, so using the information we find in the Notation Reference we add

>     \mergeDifferentlyHeadedOn
>     \mergeDifferentlyDottedOn

to the start of that section and

>     \mergeDifferentlyHeadedOff
>     \mergeDifferentlyDottedOff

to the end, giving:

These overrides have merged the two F-sharp notes, but not the two on D. Why not? The answer is there in the same section in the Notation Reference – notes being merged must have stems in opposite directions and two notes cannot be merged successfully if there is a third note in the same note column. Here the two D’s both have upward stems and there is a third note – the C. We know how to change the stem direction using `\stemDown`, and the Notation Reference also says how to move the C – apply a shift using one of the `\shift` commands. But which one? The C is in voice two which has shift off, and the two D’s are in voices one and three, which have shift off and shift on, respectively. So we have to shift the C a further level still using `\shiftOnn` to avoid it interfering with the two D’s. Applying these changes gives:

>     rhMusic = \relative {
>       \new Voice {
>         r2 c''4.\( g8 |
>         \once \override Tie.staff-position = #3.5
>         bes1~ |
>         \bar "||"
>         \time 6/4
>         bes2.\tempo "Moderato" r8
>         \mergeDifferentlyHeadedOn
>         \mergeDifferentlyDottedOn
>         % Start polyphonic section of four voices
>         <<
>           { c,8 d fis bes a }  % continuation of main voice
>           \new Voice {
>             \voiceTwo
>             % Move the c2 out of the main note column
>             % so the merge will work
>             c,8~ \shiftOnn c2
>           }
>           \new Voice {
>             \voiceThree
>             % Stem on the d2 must be down to permit merging
>             s8 \stemDown d2
>           }
>           \new Voice {
>             \voiceFour
>             s4 fis4.
>           }
>         >> |
>         \mergeDifferentlyHeadedOff
>         \mergeDifferentlyDottedOff
>         g2.\)  % continuation of main voice
>       }
>     }

>     lhMusic = \relative {
>       r2 <c' g ees>2( |
>       <d g, d>1)\arpeggio |
>       r2. d,,4 r4 r |
>       r4
>     }

>     \score {
>       \new PianoStaff <<
>         \new Staff = "RH"  <<
>           \key g \minor
>           \rhMusic
>         >>
>         \new Staff = "LH" <<
>           \key g \minor
>           \clef "bass"
>           \lhMusic
>         >>
>       >>
>     }

Nearly there. Only two problems remain: The downward stem on the merged D should not be there, and the C would be better positioned to the right of the D’s. We know how to do both of these from the earlier tweaks: we make the stem transparent, and move the C with the `force-hshift` property. Here’s the final result:

>     rhMusic = \relative {
>       \new Voice {
>         r2 c''4.\( g8 |
>         \once \override Tie.staff-position = #3.5
>         bes1~ |
>         \bar "||"
>         \time 6/4
>         bes2.\tempo "Moderato" r8
>         \mergeDifferentlyHeadedOn
>         \mergeDifferentlyDottedOn
>         % Start polyphonic section of four voices
>         <<
>           { c,8 d fis bes a }  % continuation of main voice
>           \new Voice {
>             \voiceTwo
>             c,8~
>             % Reposition the c2 to the right of the merged note
>             \once \override NoteColumn.force-hshift = #1.0
>             % Move the c2 out of the main note column
>             % so the merge will work
>             \shiftOnn
>             c2
>           }
>           \new Voice {
>             \voiceThree
>             s8
>             % Stem on the d2 must be down to permit merging
>             \stemDown
>             % Stem on the d2 should be invisible
>             \tweak Stem.transparent ##t
>             d2
>           }
>           \new Voice {
>             \voiceFour
>             s4 fis4.
>           }
>         >> |
>         \mergeDifferentlyHeadedOff
>         \mergeDifferentlyDottedOff
>         g2.\)  % continuation of main voice
>       }
>     }

>     lhMusic = \relative {
>       r2 <c' g ees>2( |
>       <d g, d>1)\arpeggio |
>       r2. d,,4 r4 r |
>       r4
>     }

>     \score {
>       \new PianoStaff <<
>         \new Staff = "RH"  <<
>           \key g \minor
>           \rhMusic
>         >>
>         \new Staff = "LH" <<
>           \key g \minor
>           \clef "bass"
>           \lhMusic
>         >>
>       >>
>     }

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