A chant is the iterative speaking or singing of words or sounds, often primarily on one or two main pitches called reciting tones. Chants may range from a simple melody involving a limited set of notes to highly complex musical structures, often including a great deal of repetition of musical subphrases, such as Great Responsories and Offertories of Gregorian chant. Chant may be considered speech, music, or a heightened or stylized form of speech. In the Late Middle Ages, some religious chant evolved into song.