What does the word undertone mean?

Usage examples for undertone

  1. Leo and Wanda had withdrawn into the deep recess of the centre window, and were talking eagerly, but in a low voice, while the Princess was also carrying on a conversation in an undertone with her brother. – Under a Charm, Vol. II. (of III) A Novel by E. Werner
  2. " Matter enough," said Peter in a guarded undertone. – Captivating Mary Carstairs by Henry Sydnor Harrison
  3. " We'll not get much of a story here," Jerry commented in an undertone. – The Clock Strikes Thirteen by Mildred A. Wirt