From 1857 to 1862, Brahms took various appointments and traveled but refused to take on a long-term professional position. The 1859 premiere in Leipzig of the Piano Concerto in D Minor was disastrous. The years conducting choirs in Hamburg were the key to Brahms's musical maturity. By 1860, Brahms had developed his mature musical voice—Romantic melody and harmony objectively constrained by Classical formal structures.