Shortly after a performance at the Hollywood Bowl in July 1942, Rachmaninoff was suffering from lumbago and fatigue. He informed his doctor, Alexander Golitsyn, that the upcoming 1942–43 concert season would be his last in order to dedicate his time to composition. The tour began on 12 October 1942 and the composer received many positive reviews from critics despite his deteriorating health. Rachmaninoff and his wife Natalia were among the 220 people who became naturalised American citizens at a ceremony held in New York City on 1 February 1943. Later that month he complained of persistent cough and back pain; a doctor diagnosed him with pleurisy and advised that a warmer climate would aid in his recovery. Rachmaninoff opted to continue with touring, but felt so ill during his travels to Florida that the remaining dates were cancelled and he returned to California by train, where an ambulance took him to hospital. It was then that Rachmaninoff was diagnosed with an aggressive form of melanoma. His wife took Rachmaninoff home where he reunited with his daughter Irina. His last appearances as a concerto soloist—Beethoven's First Piano Concerto and his "Rhapsody on a Theme of Paganini"—were on February 11 and 12 with the Chicago Symphony Orchestra under the baton of Hans Lange, and his last recital, given on February 17 at the Alumni Memorial Gymnasium/Auditorium at the University of Tennessee in Knoxville, Tennessee, included the Piano Sonata by Chopin, which contains a funeral march.