It hummed softly, content to be in service to its master.

The good doctor was sitting at his desk, humming softly while working on the project that he had been given.

Only the man, and the communications machine that hummed softly.

He reached the great doorway and stood there, humming softly.

I still don't get it, he thought, while under and behind him the engines hummed softly into life.

He walked over to the woman, who was humming softly.

The three men found her beside a small stream, humming softly.

More important things just now: He began to softly hum.

But she kept walking around and, at times, even humming softly.

An hour later in the car, she hummed softly while he kissed her.