What you are talking about is an "iFrame" there is a nice plugin by Pode that does this :
plugins-pode-html-pack_t69356
Her is more on iframes in general :
http://www.w3schools.com/tags/tag_iframe.asp
All that a lot of webpage developers do is make a header, a menubar, and then just an Iframe for a wordpress page.
On the upload files part, you might want to try the tutorial section. there is something you need to do on some servers to allow sound.