Titling

The word Titling, in the performing arts (opera, drama, audiovisual productions), defines the work of linguistic mediation encompassing subtitling and surtitling.
History.
Subtitling developed starting from 1917, during the silent film era, whereas surtitling has been used in the live performing arts since 1983 (at the dawning of digital systems).
With the appearance of new information systems, which opened the door to multilingual titling terminological debate started, too.
In the audiovisual system, even when more than one language was used, subtitles maintained their position unchanged for many years. The newest software technologies for mobile devices, which came out as an alternative to subtitling in cinemas, or the possibilities opened up by head-mounted displays, such as subtitle glasses, have made a revision of the technical terminology necessary also in the field of those performing arts that are reproducible on electronic devices.
Even more so, in the live performing arts, the presence of multilingual options on custom individual devices (Santa Fe Opera, 1998) or on mobile consumer devices (Teatro del Maggio Musicale Fiorentino, 2011) or on hybrid solutions (Royal Opera House Muscat, 2012), makes the spatial connotation of the term "sur-titles" inappropriate.
Terminology.
In both cases (performing arts that are reproducible on electronic devices and live performing arts), for a scientific approach the term "titling", broader and all-embracing, is preferable to define the work of linguistic mediation, without specifying whether the visualization is to be above (sur-titles) or below (sub-titles).
Sources.
 "Traduzione multimediale per il cinema, la televisione e la scena", Bologna: Clueb, 1996