In the organic world, there's a phenomenon called "assortative mating" - in which fit organisms choose to mate with fit organisms of the opposite sex - in the hope of making some super-fit babies.
After taking memetics into account it turns out that this is a specific manifestation of a more general phenomenon - in which fit heritable information finds ways to associate with other fit heritable information during recombination.
Fit memes find ways to associate with other fit memes in mashups, image macros, and mix-tapes. The phenomenon takes place with music, videos, literature, science, technology, code, fashion, and so on.
Looking back at the organic world from this new perspective we can see a similar thing happening in other areas. Gamete selection sometimes involves filtering out bad genes. Females often make sperm run an obstacle course, so only the best swimmers make it to the egg. In genetic engineering, genes are selectively recombined to form novel organisms, with the best genes from both parents.
I don't think it would be legitimate to refer to making a mix-tape as being a case of "assortative mating".
"Selective recombination" seems to be a better, more general term for this kind of phenomenon.