There are many resources which can be freely used by educators in online courses.
When using materials shared by others, there is an expectation that you share your materials as well.
Consider the banking analogy... if you take money out, you need to put money back in to keep everything working well and to avoid "overdrawing" from others' resources.
These are background music tracks I've developed to add behind presentations. You are welcome to download and use these (please use a right-mouse-click to Save Target As instead of hot-linking to these files).
You can easily create your own background music tracks by purchasing a keyboard with "auto-chord" features and then recording your own compositions.
Here are resources of videos relating to online education which I have found very useful.