Answer:

trala

Answer	Crossword Clue
TRALA	Song syllables
TRALA	Refrain part
TRALA	Airy refrain

TRALA	Sung syllables
TRALA	Refrain syllables
TRALA	Song refrain
TRALA	Happy-go-lucky refrain
TRALA	A chorus line?
TRALA	Cheery syllables
TRALA	Insouciant syllables
TRALA	Carefree refrain

TRALA	Insouciant refrain
TRALA	Carefree chant
TRALA	Musical refrain
TRALA	Singing syllables
TRALA	"The flowers that bloom in the spring, .."
TRALA	Light refrain
TRALA	Frivolous refrain
TRALA	Lilting syllables

TRALA	Alternative to humming?
TRALA	Lilting refrain
TRALA	Refrain from singing?
TRALA	Singsong syllables
TRALA	"The flowers that bloom in the spring, ..."
TRALA	Musical phrase
TRALA	Simple musical refrain
TRALA	Nonsensical refrain

TRALA	A chorus line
TRALA	Musical syllables
TRALA	Carefree song syllables
TRALA	Cheery chant
TRALA	Cheery refrain
TRALA	Skipping syllables
TRALA	Merry refrain
TRALA	Song sounds

TRALA	Flippant phrase
TRALA	Singer's syllables
TRALA	"Mikado" refrain
TRALA	Refrain sounds
TRALA	Vocalizer's syllables