Kanye West has called himself the greatest living rock star, and his latest pupil seems to be taking that idea as gospel. On his major-label debut, Travis Scott — a 23-year-old from Houston who’s usually shirtless if he isn’t wearing all-black – doesn’t rap so much as scream, moan and yelp like he’s fronting an Eighties hardcore band. Not the straight-edge kind, though: “Popping pills is all we know,” he tells us on his single “Antidote.” Scott has a flair for roping far-flung guests into his punk underworld. Justin Bieber sounds trashed on confidence rapping alongside Young Thug on “Maria I’m Drunk,” and Toro Y Moi’s chill synth-pop turns into demonic funk on the Pharrell-produced “Flying High.” But left on his own, Scott can grow tiresome. “I Can Tell” sounds monochromatic without another voice to push this astute curator. Some rock stars are better leading bands than going solo.