J.S. Bach - Concerto in D minor after Alessandro Marcello, BWV 974, II: Adagio

Performed by Glenn Gould. Recorded at Eaton's Auditorium, Toronto, Canada, on Monday, June 11th, 1979.

Enormous thanks to Mother Chimney for the tip on this one. And thanks as well to Christian Grey:

When I wake it's still dark. ... I hear music. The lilting notes of the piano, a sad, sweet lament. Bach, I think, but I'm not sure. ... I wrap the duvet around me and quietly pad down the corridor toward the big room. Christian is at the piano, completely lost in the melody he's playing. His expression is sad and forlorn, like the music. His playing is stunning. ... He's such an accomplished musician. He sits naked, his body bathed in the warm light cast by a solitary freestanding lamp beside the piano. ... I'm mesmerized, watching his long, skilled fingers as they find and gently press the keys, thinking how those same fingers have expertly handled and caressed my body. I flush and gasp at the memory and press my thighs together. ... I notice now that he's wearing PJ pants. He runs his fingers through his hair and stands. "You should be in bed," he admonishes.

"That was a beautiful piece. Bach?"

"Transcription by Bach, but it's originally an oboe concerto by Alessandro Marcello."

"It was exquisite, but very sad, such a melancholy melody." 

--excerpt from Fifty Shades of Grey by E.L. James, Vintage Books, London, 2011.

I'd also like to mention that the Picardy third at the end reminded me of yet another church bell classic.
 
One is also reminded of this, of course: