Back in the 1960s, the company performed the work in three seasons. Those performances started at 8 p.m., which is when typical three-hour opera performances generally started then. Let's assume that they ended around 11:30 and had two intermissions totaling 45 minutes, although I do not have timings for these performances. These assumptions imply an opera with less than three hours of music.
What could they have possibly cut? Well, I don't know for sure, but here is some speculation, after which I will ask.
- Ballet music. I myself would start here, with the dances in Act III by the laborers, the farmers, and the builders. There's a ballet in Act IV someplace before "Nuit d'ivresse."
- But I hope they wouldn't cut the Royal Hunt & Storm, the best-known ten minutes of the opera, despite Berlioz's staging demands. Only the terrible Choudens score was available then, so I'm also curious about the placement of the Royal Hunt & Storm: at the beginning or end of Act IV?
- You could cut a verse here and there from various arias and duets, perhaps from the Didon/Anna duet in Act III. You could cut a verse from "Nuit d'ivresse," but I hope not, and possibly shorten the extremely long introduction to the scene.
- There is a little slack in the grand ceremonies of Act I; it might occur to some that you could remove the scene with Andromache and her son, who never sing a word.
- I've heard some of a heavily-cut French concert performance that made some startling cuts in Act I. Well, startling if you've only heard this work uncut, anyway.