Possible Clues:

• Crosby and Vallee, e.g.
• Crosby and Como
• Crosby and Sinatra
• Como and Crosby, say, peevish for the most part accepting pound note
• Ronald arranges score for singers
• Singers with silky voices
• Many supper-club headliners
• Inquest lawyers having gold swapped for singers
• Singers
• Smooth singers