At the risk of DJ-splaining, a medley is a varied mixture of people or things; a miscellany, like a bag of frozen mixed vegetables or a 4 AM tavern. (Remember those?)
To mash up is to mix or combine two or more different elements, like a bag of miscellaneous meat parts and a bag of frozen Asian style vegetables. In this case, by definition, the following qualifies as both a medley and a mash up.
And now, a mash up.