Q:

Is there a way to get two songs on a single page using lilypond-book?

I am currently using Frescobaldi to edit my lilypond files. I have several short songs (a half-page or less) that I would like to combine into a set with more than one song on each page.  Currently, the only solution I've found is to use \book part{}, but that creates a single pdf with one song per page. Right now, in a seven-song set, everyone has to layout seven sheets of paper across the table to see everything and it would be nice if I could reduce it to three pages or so.  

A:

You can just put several scores below each other. Each of them can have an own \header. You cannot use title or composer here, but you can use the piece option to give each of these scores a title. 
\version "2.19.83"

\header {
  title = "A couple of songs"
  tagline = ##f
}

\score {

  \header {
    piece = \markup { \vspace #'2 \fill-line { \bold \huge "The first song" } }
  }

  \new Staff \with {
    instrumentName = "Soprano"
  } \relative c' {
    c4 d e f g1 \bar "|."
  }

}

\score {

  \header {
    piece = \markup { \vspace #'2 \fill-line { \bold \huge "The second song" } }
  }

  \new Staff \with {
    instrumentName = "Soprano"
  } \relative c' {
    c4 d e f g1 \bar "|."
  }

}

If you need every song to have a title and a composer, it may be easier to just set print-all-headers = ##t in the \paper block (see this link).
\version "2.19.83"

\paper {
  print-all-headers = ##t
}

\header {
  tagline = ##f
}

\score {

  \header {
    title = "The first song"
    composer = "C. Omposer"
  }

  \new Staff \with {
    instrumentName = "Soprano"
  } \relative c' {
    c4 d e f g1 \bar "|."
  }

}

\score {

  \header {
    title = "The second song"
    composer = "C. Omposer"
  }

  \new Staff \with {
    instrumentName = "Soprano"
  } \relative c' {
    c4 d e f g1 \bar "|."
  }

}

