How does a musician accompanying an opera memorize such a long score?

It takes practice to make perfect. In an opera, there are quite a few choruses, but not every actor has a chorus, and those that do are a few actors. Starting with the actors learning to sing the parts, the next step is to wind up singing. To practice singing over and over again, the strings accompany the actor to practice. Focus on singing, some to be carved, no less than dozens of times, or even hundreds of times. This process, the actor skilled in the strings of the door, the zither master, but also when it is not tired of following the actor to practice.

Over time, the masters of the strings will lose the sheet music, printed in the brain.

A lingo of the opera troupe: "The actors follow the orchestra when filming, and the orchestra watches (follows) the actors when performing."

This is to say, when filming, the actors should be meticulous with the band's score; performance band to be flexible, with the actors fast, slow or lose words and phrases when the full force of the actors to follow the actors, absolutely not allowed to throw the actors on the stage, self-concerned about pulling the strings. Because the actors on stage directly in front of the audience, instantaneous changes, to complement each other loopholes, the band should always highlight a "companion" word, to understand the duties of the accompanist. The reason why a good musician is called good is that the musicians and the actors are so 'sticky' that there are no gaps to be seen. It's a tight fit. "To" very well, following the actor fast or slow, watertight, this is the highest state of the musician.