Looser Classical

For classical music, try putting British composer Purcell's [1659-1695] opera 'The Fairy Queen' on and relaxing or as background music. It has great orchestra work and lovely voices. It's very accessible and lovely, a bit like Handel or like Mozart-style [quiet/slow version] vocals.

If you prefer more earthy music, try this excellent, long set of laid-back but refined Spanish guitar music from the Baroque and Renaissance periods. Even people unaccustomed to listening to guitar will enjoy this--just think of it as low, easy strings sections, because it sounds incredible.

If all that is still too structured, you can always try a selection of imagined 'Music from Ancient Rome'. It's quite interesting and unpredictable. Very lively and invigorating, especially for anyone who enjoys 'modern' [ie. post-Stravinsky] classical music.