“Look at Wrist” contains multitudes. It’s an incredible turnup song, its barest-bones bass-drum structure sharpened like a skeleton key to lock away your nagging prefrontal cortex. That part of the brain is sealed off for just under four minutes, each repetition of the word “wrist” another brick in the wall. Then there’s that laser-beam, doppler-radar, game-over, powering-down synth, a Pavlovian trigger to start jumping around and whipping your wrist in circles. But “Wrist” isn’t just a party track. Its spontaneity and immediately apparent authenticity, from ilovemakonnen and KEY!’s one-take verses to Dexter’s one-shot video, are codes that the industry, for all its trying, still hasn’t cracked. “Look At Wrist” gave the entire world an unvarnished glimpse into a simmering rap subculture as it began to boil; unless you read the right blogs, such glimpses were rare (and hardly ever went as viral). The song’s organic reach and rapturous reception epitomized hip-hop’s SoundCloud era, wher...