What is a concert version?

An opera is said to be performed in a concert version when it is presented without staging, sets, or costumes. The orchestra is no longer in the pit but on stage, fully visible, as in a symphonic concert. Like soloists, the singers face the audience, standing side by side. They sometimes hold their scores in hand. Entrances and exits are often observed as they would be in a traditional opera performance.

There is a variation halfway between a fully staged opera and a concert version, known as a semi-staged version. While still without sets (or sometimes using simple panels as a backdrop), the performers move around the stage and act out their roles, though without wearing costumes.