Maybe try Celibidache's Bruckner?
It's the only Bruckner I personally can appreciate, when I'm in that mood..
That describes modern performance practice more than 20th century performance practice. I guess the old school wasn't old school.
Michael Tippett's penultimate work "The Rose Lake" inspired by a trip to Lake Retba (northwest Africa).
A fantastic piece to chill with. Not going to try to describe it other than it is both beautiful and interesting :)
Chandos has the best recording below under Richard Hickox
And Lake Retba
Rihm's Symphony 'Nahe Fern' recently released on Harmonia Mundi.
This is a wonderful example of modern yet very accessible orchestral music. Those who are familiar with Rihm know his music can be starkly modern and jagged one moment and then very romantic the next. This, his latest orchestral work is much more romantic in tone and structure. Romantic because it is a homage, or more accurately a 'response' to the Brahms 4 symphonies. Four parts responding to the 4 symphonies respectively with an added part (2nd movement) song based on a Goethe poem from where the title comes from. Lovely spacious sound.