Please only use music you have permission to use.
When embedding videos from services like YouTube, that’s all gravy. Any material which isn’t allowed to be streamed will not be available to the viewer. For example, YouTube blocks certain videos in certain countries or does not allow embedding.
There are licenses available for public use of music depending on where your audience is based. This gets complicated when dealing with a global audience in many different regions.
The online medium is still somewhat of a grey area so please wherever possible use generic copyright free, royalty free material.