3.6 Extracting musical information

In addition to creating graphical output and MIDI, LilyPond can display musical information as text.

3.6.1 Displaying LilyPond notation

Displaying a music expression in LilyPond notation can be done with the music function \displayLilyMusic. To see the output, you will typically want to call LilyPond using the command line. For example,

{
  \displayLilyMusic \transpose c a, { c4 e g a bes }
}

will display

{ a,4 cis4 e4 fis4 g4 }

By default, LilyPond will print these messages to the console along with all the other LilyPond compilation messages. To split up these messages and save the results of \displayLilyMusic, redirect the output to a file.

lilypond file.ly >display.txt

Note that LilyPond does not just display the music expression, but also interprets it (since \displayLilyMusic returns it in addition to displaying it). Just insert \displayLilyMusic into the existing music in order to get information about it.

To interpret and display a music section in the console but, at the same time, remove it from the output file use the \void command.

{
  \void \displayLilyMusic \transpose c a, { c4 e g a bes }
  c1
}

3.6.2 Displaying scheme music expressions

See (extending)Displaying music expressions section ‘Displaying music expressions’ in Extending.

3.6.3 Saving music events to a file

Music events can be saved to a file on a per-staff basis by including a file in your main score.

\include "event-listener.ly"

This will create file(s) called ‘FILENAME-STAFFNAME.notes’ or ‘FILENAME-unnamed-staff.notes’ for each staff. Note that if you have multiple unnamed staves, the events for all staves will be mixed together in the same file. The output looks like this:

0.000   note     57       4   p-c 2 12
0.000   dynamic  f
0.250   note     62       4   p-c 7 12
0.500   note     66       8   p-c 9 12
0.625   note     69       8   p-c 14 12
0.750   rest     4
0.750   breathe

The syntax is a tab-delimited line, with two fixed fields on each line followed by optional parameters.

time  type  …params…

This information can easily be read into other programs such as python scripts, and can be very useful for researchers wishing to perform musical analysis or playback experiments with LilyPond.

Known issues and warnings

Not all lilypond music events are supported by ‘event-listener.ly’. It is intended to be a well-crafted “proof of concept”. If some events that you want to see are not included, copy ‘event-listener.ly’ into your lilypond directory and modify the file so that it outputs the information you want.

This document was generated by gub on July 13, 2020 using texi2html 1.82.

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