Re: Appoggiatura in bass clef at start of piece

[Peter Mitton]

Excellent explanation and many thanks Jean (and apologies again Harm for failing to understand the significance of the placement of the time and clef in your suggestion).

I was indeed misunderstanding the significance of where I was placing the time and clef expressions.  I now have a better understanding of how the voices work sequentially and in parallel. Mentally I hadn’t understood that within the parallel sections ALL expressions are running in parallel. I think I was fixed on the idea that some expressions are operating in a more privileged way - my mistake.

I’ve just been a subscriber to this group for a couple of weeks and already I’ve greatly increased my understanding of Lilypond. I’m grateful to all the people who develop Lilypond and also are willing to provide such clear assistance to technical queries.

It’s testament to the robustness of Lilypond that I’ve already transcribed about 150 short examples (over about 6 months) from a 19th century music book without problem by just reading the documentation when needed and haven’t been stumped up to now.

Thanks again for your time and dedication.

Pete

On 27 Oct 2022, at 10:50, Jean Abou Samra <jean@abou-samra.fr> wrote:

Le 27/10/2022 à 11:17, Peter Mitton a écrit :

Thanks, Harm,

Sorry, I seemed to have missed out the most important part of the challenge! Apologies. This is a simplified extract of the lower staff from the start of a two staff piano arrangement that requires 4 voices.

It’s the addition of the second voice that causes the additional treble clef to appear,  with a single voice there is no problem. But when you add a second…

\version "2.22.2"

\new Staff {
  <<
    \time 6/8
    \clef bass
    \new Voice = "a" {
      \voiceFour
      %\time 6/8 \clef bass
      \appoggiatura c,8 c2. \appoggiatura c,8 c2.
    }
    \new Voice = "b" {
      \voiceThree
      \grace s8  e2. \grace s8 e2.
    }
  >>
}

It renders as the attached file.

Which is not what I expect or want. Even an empty second voice with no notes also displays the extra clef and ledger lines and misplaces the grace note before the time signature.

The documentation on Grace notes <https://lilypond.org/doc/v2.22/Documentation/notation/special-rhythmic-concerns#grace-notes> says "Grace note synchronization can also lead to surprises. Staff notation, such as key signatures, bar lines, etc., are also synchronized. “ which I take as developer-speak for “Here be dragons”.

Actually, Harm's answer also applies to this new example, but perhaps
you didn't understand what the precise rule was. Let me try to explain.

LilyPond will get confused if you have parallel music expressions
with different grace timing. The term "parallel music expressions"
here means expression1, expression2, etc. in this construct:

<<
  expression1
  expression2
  ...
>>

while these are called "sequential expressions":

{
  expression1
  expression2
  ...
}


The golden rule is: if you use parallel expressions and one has graces,
all must have graces of the same length. To balance the graces, you can
use grace skips. This is a famous problem known as issue #34.


You are doing

<<
  \time 6/8 % _expression_ 1
  \clef bass % _expression_ 2
  \new Voice "a" { \voiceFour \appogiatura c,8 ... } % _expression_ 3
  \new Voice = "b" { \voiceThree \grace s8 ... } % _expression_ 4
>>


This puts \time 6/8 and \clef bass in parallel with the musical
voices. \time 6/8 is an _expression_ of its own, but it doesn't have
grace timing in it. Thus LilyPond is confused. If you really want
to do it this way, you need to add grace skips to expressions 1
and 2 like this:

\version "2.22.2"

\new Staff {
  <<
    {
      \time 6/8
      \grace s8
    }
    {
      \clef bass
      \grace s8
    }
    \new Voice = "a" {
      \voiceFour
                                %\time 6/8 \clef bass
      \appoggiatura c,8 c2. \appoggiatura c,8 c2.
    }
    \new Voice = "b" {
      \voiceThree
      \grace s8  e2. \grace s8 e2.
    }
  >>
}



However, as Harm explained, it is probably simpler to move \time 6/8
and \clef bass out of the parallel music _expression_, into a sequential
music _expression_. Then you don't need these extra grace skips anymore.

\version "2.22.2"

\new Staff {
  \time 6/8
  \clef bass
  <<
    \new Voice = "a" {
      \voiceFour
                                %\time 6/8 \clef bass
      \appoggiatura c,8 c2. \appoggiatura c,8 c2.
    }
    \new Voice = "b" {
      \voiceThree
      \grace s8  e2. \grace s8 e2.
    }
  >>
}



Hope that's clear?

Best,
Jean