Without going into too much detail about the opera per se, let me just point out a couple of things: Tannhäuser is one of Wagner’s greatest successes and one he was unsatisfied with his whole life. His wife Cosima noted in her diary on 23 January 1883 (three weeks before Wagner died):
“He says he still owes the world Tannhäuser.”
The opera was written in 1845, had a very different version for the Paris debut in 1861, and was revised again for Vienna in 1875. The Ouverture bears Wagner’s signature in the use of the leitmotiv: those themes or musical motives that along the opera are associated with a certain character or emotion. As a matter of fact the theme that closes the opera also opens it. We’ve seen something similar in the Overture to Mozart’s Don Giovanni. Mind you, this overture – in the so called Dresden version – lasts an average of 15 minutes. When you add the introduction to the first scene, the Venus mountain, it will take almost 20 minutes before hearing the first human voice.
Richard Wagner in 1871
This may sound unimportant today, but back in 1845, when the average introduction was around 5-7 minutes, it was certainly something audiences were not that accustomed to. And this is only valid for the Dresden version. The Paris version needed to accomodate a ballet, as it was tradition in French operas. But instead of putting it in the second act – where it normally would be – Wagner put it in the form of a Bacchanal 10 minutes into the overture, bringing the orchestral part to way over 20 minutes. It’s staggering, even today!