Sitting high up in a box at Birmingham's Hippodrome Theatre is Stephen Wood.

With full concentration, his eyes dart back and forth between the computer screen before him and an annotated music score accompanying the opera which is taking place on stage.

Hidden from view, the packed audience has no idea that Stephen, a member of Welsh National Opera’s music staff, is even there. But they would soon know if he wasn’t – because Stephen is controlling the surtitles.

Opera-goers have a love/hate relationship with surtitles. Looking up at the words every few lines can be distracting – but not looking at them means you can quickly lose the plot. With opera sung in a range of languages including German, Italian, French and Russian, there are few of us multi-lingual enough to follow the story without surtitles.

And even opera sung in English can benefit from a bit of help in distinguishing the diction.

Which brings us back to Stephen hidden away in his theatre box working hard to ensure every person in the theatre can follow the story.

His actions are precise.

“There is an art to surtitling and it can be quite satisfying,” he says. “You have to concentrate a lot. You can’t miss even one surtitle as everyone would notice.

“In some theatres we can see the stage and we can see the conductor and that makes it a lot easier and more enjoyable as you feel more part of it. You can make your cues more accurate because you can see the conductor and when he is putting the upbeat and the downbeat. You can also look at the singers’ mouths and see when they are breathing.”

But Stephen, who has worked for WNO for five years, admits that even with ultimate concentration it is still possible to slip by a second or two if a surtitler is unable to see what is happening on stage.

“If you are not able to see then you just have to rely on how well you know the piece and just guess actually! In some operas, the timing can be slightly different every night and then you do have to do a bit of guesswork. And sometimes you can end up just slightly in front or slightly behind and that is frustrating.”

And the choice of words is also important.

“We hire someone to do a translation and we also hire someone to translate it into Welsh for when we are performing in Wales,” says Stephen. “They will artfully do a kind of ‘surtitle translation’ as you wouldn’t want to translate everything, especially something wordy like La bohème or Così fan tutte. If you did that there would just be a barrage of text and no-one would be able to look at the stage as they would be looking at the screen the whole time.”

For many people surtitles provide a gateway to opera, ensuring they are able to understand the actions taking place on stage.

“In a foreign language, surtitles are all important,” says Stephen. “In the days before surtitles, I don’t know how most people could follow the opera.”