Possible Clues:

• Performed at one's peak?
• Sang and cried about love and died
• Idiosyncratically vocalised exclamation directed back and forth
• Sang, guided backwards and forwards by a couple of youngsters
• Sang a couple of lines in year-old act
• 'To get at Dolly Dee from Switzerland, by the sound of it (8)'
• That was sound enough for the Swiss
• The Swiss do get up to having shouted about it
• Sang on high?: Var.
• Sang like Frank Ifield