Humming

To make a sound from the vocal chords without pronouncing any real words, with one's lips closed.

"We are humming happily along with the music."

To express by humming.

"The team ominously hummed “We shall overcome” as they came back onto the field after the break."

To drone like certain insects naturally do in motion, or sounding similarly

To buzz, be busily active like a beehive

"The streets were humming with activity."