Classical music experts: [SFW] Can you identify any movements, phrases, concerti, or other pieces that most exemplify the buildup to, and then the letdown after, an orgasm?

I recommend “Eros”, by Ludovico Einaudi.
And the answer is no.

Right off (after “Bolero”), I think of Grieg’s “The Last Spring.” It was a favorite of mine even before, ahem, associations. I know there are others and will think on it.

Oh, and some of the sexiest music ever is the lovers’ Adagio pas de deux from Khachaturian’s ballet Spartacus. Link. (I almost think it’s better with your eyes shut. Don’t listen while driving.)

Phrases, though? There are lots of pieces that have passionate crescendos and diminuendos. Opera is full of them. But a phrase doesn’t seem long enough for a meaningful, you know, experience.

I’m not an expert, but I have done quite a lot of listening over many years.

Theme tune from Benny Hill, must have extreme stamina to pull this off though.

The signature piece with this theme is the Liebestod (“Love Death”) from Tristan und Isolde by Richard Wagner. It’s an approximately 20-minute section out of a 5-hour opera. Listen carefully and you can easily hear the build-up to the climax.
The association with death, by the way, is intentional. In literature, art and music, there are numerous examples of the connection between orgasm and death. In fact, in French, orgasm is sometimes referred to as la petite mort (“little death”). Here’s the Wikipedia article about this.
Famed Czech choreographer Jiří Kylián created an acclaimed ballet with this theme. Here’s an article from the Australian Ballet that talks about this piece and gives other examples in art and literature as well.
So, it is quite easy to find examples where “death” is a veiled reference to “orgasm”. In fact, if you substitute “orgasm” for “death” in many passages in Romeo and Juliet (Shakespeare), you’ll see things in a whole new light!