It almost sounds like Zeus is humming happily to himself.

I turned away from him and headed for the galley, humming happily in a soft voice.

Humming happily to herself, Bartta took up the open sphere.

Humming happily to himself, he began drawing up a guest list.

She was humming happily when the door opened and her sister walked in.

It hummed happily when I asked for the stars nearest to the given position.

The radio was on and I was humming happily to the music.

Not understanding why, she hummed happily with each step toward the drop shaft at the end of the long corridor.

The small stout man had marched on ahead, and was now humming happily to himself.

He was happily humming a tune to himself as he worked.