These words refer primarily to ways of uttering a succession of articulate musical sounds, especially with the human voice. In singing , the sound of the words differs from speech sound in that the vowels are lengthened and the pitches clearly defined. Sing has also come to mean to produce any succession of musical sounds. One says that a bird sings , that a brook sings , or that a skilled performer can make his violin sing . By extension, a poem or a piece of imaginative prose may be said to sing when read aloud, because the cadences are pleasing to the ear in the dame way that music is.

To hum is to sing a tune, usually with the lips closed and without articulating the words. On the other hand, any somewhat monotonous, murmuring sound may be referred to as humming .

• Bees hum as they fly from flower to flower; They flywheel in the power station hums softly as it spins; The streets of the city hum with traffic.

Similar to hum , but involving singing as well, is croon . In general, this word means to sing or speak in a low, murmuring tone in a manner inducing quiet and repose: The mother crooned softly as she rocked the baby to sleep. During and since the 1930s crooning developed as a professional style of low-pitched singing that involved some humming or other individual variations.

Chant and intone are closely related and mean to sing in a solemn and somewhat uniform cadence a piece of repetitive music such as a plainsong, a psalm or a canticle. Intone suggests more gravity and less resemblance to music than does chant .

• A priest intones the words of the Mass, but a group of choirboys will chant the responses.

In its more extended meaning, to chant is to recite something repetitiously or monotonously in a sing-song manner.

• An auctioneer chants the amounts of money bid for items to be sold; Little girls chant rhymes as they skip.