Schubert’s icily haunting song cycle, a setting of the words of the German poet Heiner Müller, begins with the saddest song ever written (“Gute Nacht,” in which, in the dead of Winter, the poet, his lover’s eye having turned to another, departs his home under cover of night) and from there grows darker yet. In these 24 songs, scored for the spare, stark combination of lone singer accompanied by piano, the lovelorn poet wanders from town to town in search of solace, company, and eventually, encountering a solitary hurdy-gurdy man, decides to join him. Dietrich Fischer-Dieskau arguably delivers one of the most accomplished and nuanced performances of this intimate masterwork ever committed to record.