The note of the engines deepened, settling down.

The notes deepened and richened as it continued to grow, until at last they were full, rich, organ sounds.

The note of wryness in his voice deepened.

The throbbing note of the engine deepened and we began to move away from the pier wall.

The note of the motors deepened; the platform was making headway against the wind as it moved toward the shore.

The note of the dumper's engine deepened and there was a hydraulic whine as the truck's body began to go up.

The note of the big diesel exhaust deepened and the Firecrest began to surge forward.

Behind them, from the autopsy room, they heard the saw's note deepen as it bit into the bone.

Then the note deepened, and he felt a lurch, and knew that he was being driven away.

The engine's note deepened as the machine rattled forward with its companions.