General synonyms:
* Hum: To sing softly or with a low, continuous sound.
* Warble: To sing in a sweet, melodious way.
* Croon: To sing softly and gently.
* Chant: To sing in a rhythmic, repetitive way, often with a religious or ceremonial purpose.
* Yowl: To sing or cry out in a loud, harsh way.
* Roar: To sing in a deep, loud voice.
* Scream: To sing in a high-pitched, piercing voice.
* Shout: To sing in a loud, forceful way.
* Whisper: To sing very softly, almost inaudibly.
Formal synonyms:
* Vocalize: To produce vocal sounds, including singing.
* Intone: To speak or sing in a monotone or chanting voice.
* Enunciate: To pronounce words clearly and distinctly while singing.
* Articulate: To express oneself clearly and effectively through singing.
Informal synonyms:
* Belt out: To sing loudly and with great force.
* Hit the high notes: To sing very high notes.
* Hum a tune: To sing a song softly.
* Pipe up: To start singing, especially after a period of silence.
The best synonym for "sing" will depend on the specific context and the desired effect.