The documentary series contains the librettos of the operas performed in the theatre. It also contains librettos of the performances of operettas –rather common during the first decades of the running of the theatre, both in Catalan and Spanish–, as well as the performances of dances, mostly dating from the 19th century. The librettos include the full text of the works performed and other basic information: the distribution of the singers at the first performances of a play, the names of the directors of the orchestra, choir and band, the names of the musicians at the first music stands in the orchestra, and the date of the premiere of an opera, operetta or ballet at the theatre.

The first librettos used to have only the text in Italian, a peculiarity of the theatres in Barcelona. Around the second half of the century, the bilingual publication was widespread, the text in Italian –mainly– on the left page and the translation into Spanish on the right page.

The librettos of the G. T. del Liceu were carefully edited, by printers such as Tomàs Gorchs, Jaume Jepús, Ignasi Estivill, Vidal i Roger, Joan Baptista Pujol, Joan Oliva. The name of the translator was not usually specified, despite evidence that important names in Catalan literature did some translations. When an opera was performed again, a new edition of the libretto was not necessarily done : sometimes the cuts made in the sung or recited text were indicated, but it was never done systematically