“Butterfly Knife” is one of those songs so intense that, however much you might appreciate it, you occasionally finding yourself wish you could un-hear. There’s something about Erika M. Anderson’s voice as she sketches out the rough details of a troubled teen — affectless and somehow removed, observing the proceedings as might a ghost — that belies the gravity of her subject. Classmates say the high school goth will never go through with the suicide whose previous attempts are recorded in knife scars on the arms. A few years later, she — he? — goes through with it: “Only God can make it right / In the desert underneath the light, it’s / Twenty kisses with a butterfly knife.” In this live performance recorded for Austria’s FM4, EMA and her backing band add a piano, some vocal fuzz and a variety of other effects, drawing out the song to epic length. A worthy live performance of one of the year’s most indelible songs.