Questlove was right to be excited about the new Kendrick, which premiered on Thursday’s Tonight Show. Dubbed “Untitled 2,†the song unfurls as one long slow-burn of a crescendo, infused with the rapper’s physical and lyrical showmanship we’ve come to know and love — similar, in some respects, to the “Untitled†number that hit The Colbert Report. (Jimmy Fallon’s reaction is also appropriate.)