With the release of Run the Jewels 2 last week, El-P and Killer Mike added to the small number of major albums crafted by a single producer or production team. It may seem absurd—after all, there are plenty of underground rap records put together by one beatmaker. But very few have any kind of major profile. This isn't unreasonable; variety is a necessity, and few producers have the depth to make an entire album worth hearing, instead preferring to churn out a few iterations of the same theme over and over.

Keeping a record to one producer can easily have its own upsides, especially when it comes to consistency. A producer can build his own world—as El-P or MF Doom have done—where the sound of the album seems to exist separate from the rest of rap music altogether. Other times, they may improve upon an existing formula, as did D.C.-based boom bap auteur Oddisee. Or they parlay a local trend into a national pop sound, like Mannie Fresh.

Although few single-album producers may make it out of the gate, it seems likely to become more and more common as hip-hop returns once again becomes more independent. After all, there's less money in production than there was a decade ago; many beatmakers end up linked directly to the rapper who made them hot. 

But taking a look back, there are still a number of rap records that stood apart thanks to singular producers.