Prodigious Austrian composer (1797-1828) whose vast oeuvre comprised over 600 secular vocal works (mainly lieder), seven complete symphonies, sacred music, operas, incidental music, and a large body of piano and chamber music. Known only to a relatively small circle of admirers in Vienna during his lifetime, Schubert's international renown grew immensely in the decades after his death at the age of 31. Incredibly rare and highly sought-after ink signature, "Franz Schubert,” dated 1821, on an off-white 5.25 x 3 slip featuring a bouquet of flowers and a four-line poem. Mounted and framed to an overall size of 10.75 x 8.75, with a presentation inscription on a page affixed to the frame's backing by French artist Ferdinand Bac. Bac writes, in full (translated): "Autograph of F. Schubert. To Mr. and Mrs. de Saint-Martin I offer this modest relic as a witness to my admiration and my gratitude, Ferdinand Bac, 26th June 1937." The illegitimate nephew of the Emperor Napoleon, Bac was a prolific cartoonist known for his caricatures and a prominent admirer of Schubert's music. In fine condition.