I'm a life-long insomniac. I find some gently funky music at low volumes really helps me get to sleep or to ease back in. Late 1950s hard bop is the exact right level for me since it generally has a decent mid tempo, enough funk, and few arrangements or sharp edges. Anything too outside, arranged or too danceable (whether boogaloo or smooth jazz) just makes things worse.
At the moment, I'm using Houston Person's High Notes, which are absolutely perfectly made for insomniacs.