And a little article I stumbled upon about him.
http://www.esquire.com/news-politics/a638/esq1003-oct-sinatra-rev/
In David Niven's charming and often moving memoir, he relates a story for the ages: sailing off the coast of Los Angeles in Grant or Bogart or such's boat, when suddenly Sinatra coasts up in his own, equipped obviously with piano. They anchored together and listened to Sinatra play as the sun set and the waves lapped around them.