Possible Clues:

• Nonsense song syllables
• Interjection used to express joy or pleasure
• Short singing refrain
• Painting's returned to southern state -- hooray!
• The flowers that bloom in the spring — — (Mikado)
• Lilting song syllables
• Start of a happy-go-lucky utterance
• Refrain from singing when you're happy?
• Starting musical syllables
• Cheery sounds