If you scroll through Leven Kali’s iPhone camera roll, you’ll find old camcorder videos of him as a two-year-old toddler, wide-eyed and grinning in front of a tiny toy drum set. His mom excitedly cheers him on as he bangs the instrument, a bit off-beat. “I still have memories of that kit, the way that pedal felt and the way that the sticks would feel,” Kali tells Rolling Stone while looking at the video, smiling through his tinted sunglasses. “T…