“I am not sure I ever have ‘heard’ Brahms’s ‘Requiem’ — strictly as a member of an audience,” the incomparable California-born choral conductor Robert Shaw wrote in 1997. “At this moment I can recall only performances in which I was a participant — the first, of course, as a singer.” For his many good efforts, Brahmsian and otherwise, Shaw, who died two years later, presumably now occupies some lofty angelic perch, where he can simply sit back and take in the performance of “A German Requiem” that Robert Spano will conduct with the Atlanta Symphony Orchestra and Chorus at Carnegie Hall on Saturday, Shaw’s 100th birthday.

Shaw, who was working on an English translation of the “German Requiem” at his death, loved the work. Brahms, writing after the deaths of his mother and his surrogate father, Robert Schumann, bypassed the standard liturgical meditations on death and judgment — no Dies Irae to scare the bejesus out of listeners — and set biblical texts of his own choosing, intended to console those left behind.

Like Brahms, Shaw founded an intense spirituality on humanism rather than religiosity. Stemming from a line of evangelical ministers and seemingly destined to become one himself, he evolved instead into a fervent secular moralist, deeply flawed in personal character but immensely charismatic and inspiring in his musical evangelism.

Shaw conducted the “German Requiem” perhaps as many as 90 times, if Keith C. Burris’s “Deep River: The Life and Music of Robert Shaw” (GIA Publications, 2013), is to be believed. (But a caveat: This sprawling, numbingly repetitive book is not to be trusted on any number of other counts.)