I would like to merge all title and subtitle fields in a bib file into the field title with a custom separator. Is there a way to do this? (I know that biber has a tool mode that can be used for manipulating a source file. It is, for example, possible to resolve inheritances. But it would seem to me that merging two fields into one is not possible.)

Background: I sometimes use my bib file with pandoc. Pandoc merges the fields title and subtitle, but it uses a colon as a separator, which is rather unusual in German.

1 Answer 1



<?xml version="1.0" encoding="UTF-8"?>
    <maps datatype="bibtex" level="user">
      <map map_overwrite="1">
        <map_step map_field_source="subtitle" map_final="1"/>
        <map_step map_field_set="title" map_field_value=". " map_append="1"/>
        <map_step map_field_set="title" map_origfieldval="1" map_append="1"/>
        <map_step map_field_set="subtitle" map_null="1"/>

in a file called mergesubtitle.conf into the same directory as your .bib file.

Then call Biber with

biber --tool --configfile=mergesubtitle.conf <yourbibfile.bib>


  author = {Anne Elk},
  title = {On the Theory of Brontosauruses},
  subtitle = {Really Interesting Dinosaurs},
  date = {1970},
  publisher = {Monthy Press},
  location = {London},

is saved as brontos.bib, the call biber --tool --configfile=mergesubtitle.conf brontos.bib will result in a file called brontos_bibertool.bib with the contents

  author    = {Elk, Anne},
  location  = {London},
  publisher = {Monthy Press},
  date      = {1970},
  title     = {On the Theory of Brontosauruses. Really Interesting Dinosaurs},

being placed in the same directory.

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