for
epub3 rules instead of having a dc:date element, you need to have dcterms:modified property, which is what the error is trying to tell you.
However, I'm curious if you really want this to be an EPUB 3 document. I didn't see filetypes that would require an epub3 (such as perhaps an audio file of the drumming in this case), and if the content isn't really making use of EPUB3 capabilities then you would be much better off tagging this as an EPUB2 document.