Frank Sinatra was a functioning alcoholic, who went cold turkey on his love of booze and cigarettes in the weeks running up to recording sessions to save his voice. The late crooner's biographers, ANTHONY SUMMERS and ROBBYN SWANN, have presented evidence they discovered while researching their book SINATRA: MY LIFE to alcoholism experts, who have confirmed claims Ol' Blue Eyes was ruled by Jack Daniels. The husband-and-wife journalists now claim Sinatra's boozy standard ONE FOR MY BABY was more than just a song the legend sang; it was actually the soundtrack to his sad, lonely and violent life. Swan says, "Sinatra's use and abuse of alcohol was much more important than anyone understood. We tracked that and we gathered information that, from the mid-40s on, he was really seriously abusing the booze, and, even in his later life, drinking a bottle of Jack Daniels a day. "It was all well documented by close friends, who spoke lovingly about him. "When we submitted that evidence to a couple of experts on alcoholism, they said, pretty conclusively, that this is a functioning alcoholic and I think that helped us to explain and I think will help the reader understand the explosive temper, the up-and-down relationship with women and his children, the depressions and the insomnia." Oxford University-educated Summers adds, "One of the strange anomalies is that a man, who not only drank so much but smoked so much - those untipped Camel cigarettes - for years and years and years, was still able to put out such a wonderful voice over such a long period. "We learned that he went off the booze and off the cigarettes for a period before he made an album." Summers claims the ravages of heavy drinking and smoking took their toll on Sinatra's famous voice - and this can clearly be heard on some recordings. The biographer adds, "The booze and the cigarettes and the sorrows in his life affected his voice. "You hear him do One For My Baby in the late 50s, and then you hear the recording he did of the same song just before the 50s and they're as different as day is from night. "The voice, by then, has been tempered, weathered by the booze, the cigarettes, the sadnesses and he's clearly living the song more the second time around."