Yup, hook this up to your 360 HDD and locate the xbox 1 saves directory, (Don't recall exactl location at the moment).
It is 'theoretically' possible but hasn't been accomplished yet. The music files are stored much like the xbox1's music collection. They are 192 kbps .wma files with a special header (ID3 Tag Storage). And then finally there is a file called 'mindex' on partition3 that is basically your xbox1 'st.db' file in a way. It keeps a record of all your current music.
At the moment this doesn't look to be possible. All video files currently being stored on the hdd are within PIRS archives. Meaning they are signed and cannot be changed, therefore; we cannot create our own either.
Mainly, this is what it is. But there are lots of other fun stuff you can do with access to the HDD.

Thank you for answering my questions. Can you clear up the newest controversy of a question I have about 15 feet being the limit for a USB 2.0 cable? You've got to be kidding me.
And if that's true, then you could bypass that by buying a bunch of 2.0 USB HUBs and stringing them together, couldn't you? (FYI My 360 is about 14 feet from my nearest USB port on my PC across the hallway from my front door to under my HDTV in the stand it sits on).
Also, I am beginning to regret buying this product because it doesn't look like I'll really end up using it.
Oh well - then again I can always eBay it.
eBay couldn't pull the auction because it is an actual product, doesn't violate any MS warranties on the Xbox 360 that I know of, and isn't a "hack" nor a "mod" that allows anything illegal or in violation on the 360 (although some would consider it a hack or a mod that does allow illegal things to take place, us who know what we're talking about know this is ridiculous to call it such terms).
Then again it may allow for some things that could violate MS's policieis but if you don't do those things then you don't violate the policy so MS couldn't pull it off their site as an auction. This is obvious anyway, seeing as how it's in stores and being sold like an "action replay" essentially.