Six months after retiring from touring, Neil Diamond returned to the stage Friday night to perform a private mini-concert in honor of firefighters battling a Colorado wildfire. Despite hard work by more than 400 firefighters to douse the nearly month old Lake Christine blaze, only half of it has been contained. The 77-year-old singer visited the Incident Command post in Basalt in central Colorado with his wife Katie McNeill to meet dozens of firefighters gathered there for a fire burning. He then surprised the audience by playing "Sweet Caroline" with an acoustic guitar. The Rock and Roll Hall of Famer announced his retirement in January, revealing that he has been diagnosed with Parkinson's disease.