little
He hummed a little tune as he washed the dishes.

good, great, nice
happy, jaunty, lively, merry, upbeat, uplifting
haunting, melancholy, sad
classic, familiar, favourite/favorite, old, popular, traditional, well-known
a collection of classic tunes

catchy (informal), memorable
dance, show
folk, jazz, pop, etc.
an old jazz tune

hymn
signature (BrE), theme (esp. BrE)

hum, play (sb), sing, whistle
He softly hummed the tune to himself.
She played us a tune on the piano.

spin (informal)
DJs spinning the coolest tunes

hum along with, sing along with
compose, write
pick out
The kids were picking out a tune on the old piano.

carry, hold
He wasn't allowed in the choir because he couldn't hold a tune.

to the tune of sth
The crowd were singing ‘Give us jobs!’ to the tune of ‘Happy Birthday’.