Vera Keyes' "Let the Bright Tomorrow in" song is a holotape in the Fallout: New Vegas add-on Dead Money. It contains Vera Keyes' voice, needed to unlock the elevator to the Sierra Madre vault in Heist of the Centuries.
Rather than a cassette like most holodisks, it can be found by accessing the music controls on the receptionist's terminal, found on the desk by the front doors in the lobby of the Sierra Madre hotel. Downloading the ambient music for the restaurant, executive suites and theater will add a note to your Pip-boy. This particular note is the restaurant ambient music.
You have a Holotape of Vera Keyes' melody, "Let the Bright Tomorrow in."