I agree with both of you that channelling an mp3 player in is the easiest way to do thia.
However, if you use the SD Audio feature you can play along and record the results directly into the KN7000.
I find that a great way to do this is to use an mp3 with live drums and bass, record a little of your own backing over that and then use the results to play 'live' or to make a recording.
Katrina, you won't get great results if you want to use the rhythms in the KN7000. You can only synchronise the start of the track. So, your audio track has to be an exact 'beats per minute' in order to do that, otherwise it will run out compared with the KN7000s rhythms.
So, in practise you choose a backing track that has drums on it... or rather, to clarify, the timing of the performance has to come from the backing track, not from the KN7000. Use the KN7000 to layer over the top of the track.
Both methods have their place it depends what you're trying to achieve but if you're using SD-Audio back up your SD Card regularly. KN-SDExplorer backs up the SD Audio tracks but remember that it can only restore them to the SD Card they were backed-up from due to the unwarranted copy restrictions.
And, as an aside, use SD Favorites to load your sequences, it saves lots of fiddling about searching for the right sequence.