Viana was saying something, not in a whisper now, but as if muttering to himself.

NEWYORKER: While the Women Are Sleeping

Nothing matters to Tony except inventing things and having a good time, and Downey, muttering to himself, ignores everyone else in the movie for as long as he can.

NEWYORKER: Iron Man

Dr. Ferrara joined Genentech as a junior scientist in 1988, and his colleagues were charmed by the slightly disheveled Sicilian who drove to work on his Yamaha VMAX motorcycle and paced the hallways, muttering to himself, when his work was going well.

FORBES: The Single-Minded Sleuth