FYI: When you take the vocals from one song and layer them over the beat from another song, it’s called a ‘Blend.’ A mash-up would be combining the beat from one or both songs and using the vocals from both songs. Like the verse from one song, but the chorus from another.

For example the album Jay-Z did with Linkin Park would be considered an album of mash-ups. But, most of the remix albums of The Black Album would be considered blends.