By Joe Price & Constant Gardner

Rap as a genre is in a perpetual state of forward motion. Just as there will always be people yearning for the good old days, there will always be new generations of creators with no regard for any rules or norms—polarizing artists like Kanye West who are exploring rap's boundaries and blurring lines between genres.

As rap expands and mutates, becoming, in many cases, almost unrecognizable from the boom-bap hip-hop of the '80s, producers are at the forefront of the experimentation. Whether it's Flying Lotus with his acid-drenched, jazz-infuenced beats, Clams Casino's hazy dreamworlds, or Blue Sky Black Death's incredible versatility, there's a whole raft of adventurous producers with unique sounds and styles. Get familiar with these 20 producers who are expanding the sound of hip-hop.