Mixtapes/EPs Key! – Martin Luther Key (Mixtape) By malbin - December 30, 2015 Share on Facebook Tweet on Twitter Key! drops off a new mixtape Martin Luther Key!, boosting 15 songs with features from Playboi Carti, Keith Ape, Johnny Cinco, & others. Key! has never disappointed, and you surely won’t be if you hit play on this tape. Stream or download it below.