Bar and bar number checks

Bar checks help detect errors in the entered durations. A bar check may be entered using the bar symbol, |, at any place where a bar line is expected to fall. If bar check lines are encountered at other places, a list of warnings is printed in the log file, showing the line numbers and lines in which the bar checks failed. In the next example, the second bar check will signal an error.

\time 3/4 c2 e4 | g2 |

An incorrect duration can result in a completely garbled score, especially if the score is polyphonic, so a good place to start correcting input is by scanning for failed bar checks and incorrect durations.

If successive bar checks are off by the same musical interval, only the first warning message is displayed. This allows the warning to focus on the source of the timing error.

Bar checks can also be inserted in lyrics:

\lyricmode {
  \time 2/4
  Twin -- kle | Twin -- kle |
}

Note that bar check marks in lyrics are evaluated at the musical moment when the syllable following the check mark is processed. If the lyrics are associated with the notes of a voice which has a rest at the beginning of a bar, then no syllable can be located at the start of that bar and a warning will be issued if a bar check mark is placed in the lyrics at that position.

It is also possible to redefine the action taken when a bar check or pipe symbol, |, is encountered in the input, so that it does something other than a bar check. This is done by assigning a music expression to "|". In the following example | is set to insert a double bar line wherever it appears in the input, rather than checking for end of bar.

"|" = \bar "||"
{
  c'2 c' |
  c'2 c'
  c'2 | c'
  c'2 c'
}

When copying large pieces of music, it can be helpful to check that the LilyPond bar number corresponds to the original that you are entering from. This can be checked with \barNumberCheck, for example,

\barNumberCheck 123

will print a warning if the currentBarNumber is not 123 when it is processed.

See also

Snippets: Rhythms.