Samuel Barber's Adagio for Strings (Opus 11), first performed in 1938, is one of the most loved pieces of modern music. It was played at John F. Kennedy's funeral, but perhaps it is best understood (thanks to delanceyplace.com) as one of the twentieth century's most powerful love songs:
"Barber had met and fallen in love with his fellow-student at the Curtis Institute, the composer Gian Carlo Menotti, in the autumn of 1928 and--though you would hardly believe they were more than devoted friends from Barbara B. Heyman's otherwise thorough biography--they were to share a house as lovers for over thirty years. The summer of 1936, which Barber spent with Menotti in the Austrian mountain village of St. Wolfgang, was one of the most idyllic times either could remember, and it was toward the end of their stay there that Barber wrote to the cellist Orlando Cole: 'I have just finished the slow movement of my quartet today--it is a knockout!' When, encouraged by Arturo Toscanini, Barber made a five-part arrangement of the String Quartet's Adagio for strings orchestra and Toscanini duly conducted it, the Adagio entered the orchestral repertoire ... [and] won the praise of Barber's contemporaries. Copland praised its 'sense of continuity, the steadiness of the flow, the satisfaction of the arch that it creates from beginning to end,' asserting that 'it comes straight from the heart,' while William Schuman thought 'it works because it's so precise emotionally ... you're not aware of any technique at all.' And Virgil Thomson came closest to the reason why when he described it as 'a detailed love scene' --a fact which its subsequent memorial usage has all but obliterated."
David Nice, Elegy: Music for Strings, Scottish National Orchestra conducted by Neeme Jarvi, Notes on the Music, Chandos Records.