quiet classical music

Try searching for "tafelmusik" in your music streamer catalog or online.

I like Mike's suggestions for listening above, but for me 5 Beethoven Piano Concertos and Beethoven and Mahler symphony recordings would never remain "in the background."

Specific names in addition: Gibbons, Byrd, Telemann, Corelli, some Scarlatti, Lully, Purcell, Geminiani

https://en.wikipedia.org/wiki/List_of_Baroque_composers

@mikelavigne 

i think the point where that music can be complimentary to reading is variable, and relative to individual sensitivities and even a system's ability to play them realistically at moderate volume levels.

Agreed! For me, there is something in those pieces that refuses to recede into the background. My defenses against Beethoven are much weaker than yours.  When Beethoven masses his troops outside my gates, I'm obliged to lower the drawbridge. Telemann, however, can stand out there all night.