When I think of "soothing", string quartets come to mind. The potboiler symphonic works are generally not what I'd call soothing. Great music, yes. Soothing, not so.
Ralph Vaughan Williams'"Pastoral" symphony (#3)is soothing. His "Fantasia on a Theme by Thomas Tallis" is another "soothing" work, as is "Fantasia on Greensleeves".
Shostakovich is not what I'd call "soothing"....