Try this app
I've been using an app called "Insight" for about 2 years now. It's free and available on iTunes and Google Play/android. It's a meditation/relaxation app. It has thousands of recordings covering...
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There are optional in-app purchases but you certainly don't need to do that. There are plenty of freebies. There are also other language options so if you want to relax to a French voice whispering in your ear go right ahead :)