Related Clues:

• Cavern sounds
• Resounds
• Rebounding sound waves
• Sound reflections
• Talks back?
• Warbles
• Sings Swiss-style
• Hints of the past
• Sings in peak form?
• Displays peak singing condition?
• Serenades Heidi, maybe
• Sings in the Alps
• Falsetto songs
• Alpine refrains
• Repeats