String teary Samuel Barber’s Adagio for Strings was composed in 1935 as a movement of the composer’s String Quartet, but it achieved greater fame in the composer’s own arrangement for string orchestra, which was championed early on by conductor Arturo Toscanini. It wasn’t long before it became pigeonholed as the all but obligatory piece to be played on occasions of national mourning. The San Diego-based writer Thomas Larson shines his spotlight on this composition in The Saddest Music Ever Written, published by Pegasus Books. A resident of Santa Fe some decades ago and an arts writer for The Santa Fe New Mexican from 1980 to 1982, Larson has previously turned his authorial attention to the art of the memoir. The Saddest Music Ever Written is perhaps best approached as an example of that genre, though one that reaches, with speculative specificity, to imagine how his parents and grandmother must have reacted to this music on historic occasions at which it was heard and how it must have reflected aspects of their lives. These reminiscences are interspersed with a recounting of Barber’s life and of observations about the Adagio’s history and its musical content, as well as sections in which Larson lays down guidelines about how one ought to write about music and how the Adagio ought to be played. He enjoys drawing up lists: movies that use the Adagio as a soundtrack, composers who have written for string orchestra, other pieces that qualify as sad (if not as sad as Barber’s). In casting his book as a “hybrid narrative,” Larson allows himself free rein in terms of structure and style. The tone of his writing is vernacular and talkative, and that aspect of it will probably come off well when he presents a reading at 6 p.m. on Friday, Oct. 8 at Collected Works Bookstore (202 Galisteo St., 988-4226).