Amazon has a page of free music downloads. You can save them to your computer and listen to them offline, save them to your phone or tablet or any other device that plays music. This is a list that is really all free.
There’s a real variety. I picked some soothing Celtic music, some meditation ones, but there’s a lot to choose from. There are children’s songs, patriotic songs, ethnic songs, inspirational music, bible stories, and some modern tunes.