\NeedsTeXFormat{LaTeX2e}
\documentclass[10pt]{letter}
\usepackage{geometry}
\geometry{a4paper,noheadfoot,nomarginpar,left=1.5cm,right=1.5cm,top=1.5cm,bottom=1.5cm}
\usepackage{fontspec}
\defaultfontfeatures{Ligatures=TeX}
\usepackage{polyglossia}
\setdefaultlanguage[spelling=old]{german}
\setmainfont{CMU Serif}
\setsansfont{CMU Sans Serif}
\setmonofont{CMU Typewriter Text}
\usepackage{graphicx}

\def\tmpNameFull{tmplily.ly}       \newwrite\tmpFileFull
\def\tmpNameHead{tmplilyhead.ly}   \newwrite\tmpFileHead
\def\tmpNameTail{tmplilytail.ly}   \newwrite\tmpFileTail
\def\tmpNamePaper{tmplilypaper.ly} \newwrite\tmpFilePaper
\def\tmpNamePdf{tmplily.pdf }

\def\tmpfragprefix{tmplilyfrag}

\def\lilycommand{/mypath/to/lilypond }
\def\lilyparms{ --bigpdf }

\newcount\fragcount

{
  \catcode`|=0 \catcode`[=1 \catcode`]=2 \catcode`\#=12
  \catcode`\{=12 \catcode`\}=12 \catcode`\\=12
  |gdef|eofull[\end{lilyfull}]
  |gdef|eohead[\end{lilyhead}]
  |gdef|eofrag[\end{lilyfrag}]
  |gdef|eotail[\end{lilytail}]
  |gdef|hashtag[#]
  |gdef|escape[\]
  |gdef|definepaper[\definepaper]
]

{
  \obeylines
  \gdef\doline#1
  {
    \def\oneline{#1}
    \ifx\oneline\eofull
       \def\next{\end{lilyfull}}
    \else
       \ifx\oneline\eohead
          \def\next{\end{lilyhead}}
       \else 
          \ifx\oneline\eofrag
             \def\next{\end{lilyfrag}}
          \else 
             \ifx\oneline\eotail
                \def\next{\end{lilytail}}
             \else 
                \ifx\oneline\definepaper
                   \immediate\write\tmpFile{\escape include "\tmpNamePaper"}
                   \let\next\doline
                \else
                   \immediate\write\tmpFile{\oneline}
                   \let\next\doline
                \fi
             \fi
          \fi
       \fi
    \fi
    \next%
  }
}

\makeatletter

\newenvironment{lilyfull}[2]{
  \global\advance\fragcount by 1
  \immediate\openout\tmpFileFull=\tmpNameFull
  \gdef\tmpFile{\tmpFileFull}
  \immediate\openout\tmpFilePaper=\tmpNamePaper
  \immediate\write\tmpFilePaper{\hashtag(set!
     paper-alist (cons '("mySize" . (cons (* #1) (* #2))) paper-alist))}
  \immediate\closeout\tmpFilePaper
  address@hidden
}{
  \immediate\closeout\tmpFileFull
  \immediate\write18{\lilycommand \lilyparms \tmpNameFull}
  \immediate\write18{pdfcrop \tmpNamePdf \tmpfragprefix\the\fragcount.pdf}
  \begin{center}\includegraphics{\tmpfragprefix\the\fragcount.pdf}\end{center}
}

\newenvironment{lilyfrag}[2]{
  \global\advance\fragcount by 1
  \immediate\openout\tmpFileFull=\tmpNameFull
  \gdef\tmpFile{\tmpFileFull}
  \immediate\write\tmpFileFull{\escape include "\tmpNameHead"}
  \immediate\openout\tmpFilePaper=\tmpNamePaper
  \immediate\write\tmpFilePaper{\hashtag(set!
     paper-alist (cons '("mySize" . (cons (* #1) (* #2))) paper-alist))}
  \immediate\closeout\tmpFilePaper
  address@hidden
}{
  \immediate\write\tmpFileFull{\escape include "\tmpNameTail"}
  \immediate\closeout\tmpFileFull
  \immediate\write18{\lilycommand  \lilyparms \tmpNameFull}
  \immediate\write18{pdfcrop \tmpNamePdf \tmpfragprefix\the\fragcount.pdf}
  \begin{center}\includegraphics{\tmpfragprefix\the\fragcount.pdf}\end{center}
}

\newenvironment{lilyhead}{
  \immediate\openout\tmpFileHead=\tmpNameHead
  \gdef\tmpFile{\tmpFileHead}
  address@hidden
}{
  \immediate\closeout\tmpFileHead
}

\newenvironment{lilytail}{
  \immediate\openout\tmpFileTail=\tmpNameTail
  \gdef\tmpFile{\tmpFileTail}
  address@hidden
}{
  \immediate\closeout\tmpFileTail
}

\makeatother

\def\lorem{
  Lorem ipsum dolor sit amet, consectetur adipiscing elit, sed do eiusmod tempor incididunt ut
  labore et dolore magna aliqua. Ut enim ad minim veniam, quis nostrud exercitation ullamco 
  laboris nisi ut aliquip ex ea commodo consequat. Duis aute irure dolor in reprehenderit in 
  voluptate velit esse cillum dolore eu fugiat nulla pariatur. Excepteur sint occaecat cupidatat 
  non proident, sunt in culpa qui officia deserunt mollit anim id est laborum.
}

\begin{document}
\pagestyle{empty}

\begin{lilyhead}
\version "2.18.2"
\include "deutsch.ly"
\pointAndClickOff
\definepaper
\paper {
  #(set-paper-size "mySize") left-margin = 1\cm top-margin = 0\cm bottom-margin = 0\cm 
  line-width = #(- paper-width (* 1 cm) ) indent = 0 page-count = #1  ragged-right=##t
  ragged-bottom = ##t ragged-last-bottom = ##t annotate-spacing=##f
}
\header {
  tagline = ##f
}
#(set-global-staff-size 17)
allowGrobCallback = #(define-scheme-function (parser location syms) (symbol-list?)
  (let ((interface (car syms)) (sym (cadr syms))) #{ \with { \consists #(lambda (context)
  `((acknowledgers . ((,interface . ,(lambda (engraver grob source-engraver)
  (let ((prop (ly:grob-property grob sym))) (if (procedure? prop) 
  (ly:grob-set-property! grob sym (prop grob))))))))))}#}))
absFontSize = #(define-scheme-function (parser location pt)(number?)
  (lambda (grob) (let* ((layout (ly:grob-layout grob))
  (ref-size (ly:output-def-lookup (ly:grob-layout grob) 'text-font-size 12)))
  (magnification->font-size (/ pt ref-size))))) 
\score { <<
\end{lilyhead}

\begin{lilytail}
  >>
  \layout {
    \context {
      \Score
      \allowGrobCallback font-interface.font-size
      \omit BarNumber
    }
    \override Lyrics.LyricText  #'font-name = #"CMU Serif"
    \override LyricText.font-size = \absFontSize #10
    \override StanzaNumber.font-name = #"CMU Serif Extra"
    \override StanzaNumber.font-size = \absFontSize #10
    \override StanzaNumber.font-name = #"CMU Serif"
    \override StanzaNumber.font-size = \absFontSize #10
  }
}
\end{lilytail}

\lorem

\begin{lilyfrag}{15 cm}{10.0 cm}
\relative c'{\key c \major \time 4/4 \partial 8 c8^\p fis g4. ~ g4.  c,8^\mf  
\tuplet 3/2 {fis4 g a} \tuplet 3/2 {fis g a} fis8 g4. ~ g4.} 
 \addlyrics { Ma -- ri -- a, __ I've just met a girl named Ma -- ri a, __}
\new PianoStaff <<
\new Staff = "upper" {\skip8\skip1\skip1\skip2..}
\new Staff = "lower" {\clef bass \skip8\skip1\skip1\skip2..}
>>
\end{lilyfrag}

\lorem

\begin{lilyfrag}{15 cm}{4.0 cm}
 \relative c'{\key c \major \time 4/4 \autoBeamOff \partial 8 c8 a'4 a8 a [g] a b4 (g8) e4} 
 \addlyrics { In ei -- nem küh -- len Grun -- de, }
\end{lilyfrag}

\lorem

\begin{lilyfrag}{15 cm}{2.0 cm}
\relative c'{\key c \major \time 4/4 c2 b'2 a4. f8 d2}
 \addlyrics { There's a place for us }
\end{lilyfrag}

\lorem

\begin{lilyfrag}{15 cm}{2.0 cm}
\relative c'{\key c \major \time 4/4 c2 c'2 h4 g8 a h4 c}
\addlyrics { Some -- where o -- ver the rain -- bow }
\end{lilyfrag}

\lorem
\end{document}