Masak_aer....I've just discovered Celtic Woman. It comes in DD 5.1 dvd or cd form. GET IT! It's as beautiful and relaxing as any music I've ever heard. It's available for ~12 bucks for the cd on ebay ($75 if you buy from PBS). Basically, 5 Irish angels play and sing wonderful new and a bit of traditional Celtic music. Even if you don't like traditional Celtic stuff, this will thrill you...very etherial. A full orchestra and chorus backs up these lovely lassies.
JUST BUY IT...and I recommend the DVD because these ladies are really wonderful to watch.
You'll thank me. You'll drift away on wonderfully flights of relaxation. Only a couple of tracks are 'upbeat' enough to stir you from your quiet enjoyment. (The only problem with using for sleep might be the ovations from the audience, as it's recorded live in Ireland. But it's not overwhelming noise.) And give a copy to your cousin!