The renowned septet from Offenbach’s final work is of uncertain origin. It was not in the original score and its source remains a riddle. The opera was written for the Opéra-Comique and was to have spoken dialogues. It was incomplete at the composer’s death in 1860. Ernest Guiraud completed the piece and added the recitatives. The poor guy has been on the pointy end of criticism ever since. I think he did as good a job as can be expected under the circumstances.
Guiraud was a fine musician. Born in New Orleans, his father Jean-Baptiste-Louis Guiraud also a musician had won the Prix de Rome. He sent his soon to Paris where he completed his musical education and also won the Prix de Rome – the only example of a father and son to do so. For many years he was a professor at the Paris Conservatoire. He also set the recitatives in Carmen to music. This too has contributed to the abuse casually sent his way.
Back to the septet. It’s set for six singers, so why septet? The chorus is counted as a participant, hence septet. Sounds weak, but that’s the way it is. As to who wrote it, as indicated above there can only be a guess. But it almost always done in performance. It comes just before the end of the Venetian scene.
A word about the order of the acts. The Venetian scene was often done as Act 2. Today it typically is Act 3. I think it makes better dramatic sense to do it as the second act. Each of the three acts is a separate story, and thus could be done in any order. The intensity of the drama and the music increases as the stories unfold. The act with the doll (Olympia) is always Act 1. The scene in Munich in which Antonia sings herself to death has the most powerful music in the score. I think it should come after the Venetian act which, though it contains much beautiful music, operates on a lower dramatic level.
All of this aside, the anonymous septet is a grand piece in which all the threads of the story are presented in a wonderful ensemble based on the theme of the Barcarolle which begins the act. The tenor (Hoffmann) opens the piece and takes the musical lead during it. Placido Domingo is the Hoffmann on the recording linked below. I have included the music which follows the septet that concludes the act. This consists of the duel between Hoffman and and the wonderfully named Schlemil. Offenbach being Jewish certainly new the Yiddish meaning of the name. After he kills Schlemil Hoffmann finds that the courtesan he loves, Giulietta, has ridden of in a gondola with Pittichinaccio. The poor guy can’t catch an amorous break, which is the point of the opera. He should stick to art and leave women to men with money.