@hilde45,
'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." '
@chayro,
'If you're just going to read, might as well put on one of the classical FM or whatever radio you have and let it play.'
This is the dilemma.
We need suggestions that sound pleasant enough to drown out any ambient sounds yet also do not irritate or draw too much attention to themselves.
FM radio doesn't always do that, and then there's the presenters and ever insistence upon the "news".
I certainly wouldn't recommend the Goldberg Variations as background music. Not even the lovely Zenph re-performance of Glenn Gould's 1955 attempt.
As @mikelavigne pointed out, familiarity could be of a help here, especially to predominantly classical music fans.
It's been long known since the days of Pavlov that repetition does eventually tend to make the brain switch off somewhat.
It's just a question of finding that perfect balance.
Maybe some fans of ambient music could suggest something?
