sing

sing past tense sang, past participle sung

1

with your voice

[intransitive and transitive] to produce a musical sound with your voice:

She can sing beautifully.

Most children enjoy singing.

We had a great time singing some of the old songs.

sing to

My mother used to sing to me when I was young.

He was singing to himself quietly.

sing somebody something

Come on, sing us a song!

I've never been able to sing in tune (=sing the correct notes).

She patiently sang the baby to sleep.

➔ singing

2

birds

[intransitive] if birds sing, they produce high musical sounds:

I could hear the birds singing outside my window.

3

high noise

[intransitive always + adverb/preposition] to make a high whistling sound:

A kettle was singing on the stove.

sing past

A bullet sang past my ear.

4

sing somebody's praises

 to praise someone very much:

Mrs Edwards was singing your praises today.

5

sing a different tune

 to say something different from what you said before:

You're singing a different tune now!

6

be singing from the same hymn sheet/book

 used to say that a group of people all have the same aims or all express the same opinion on a particular subject:

Union representatives are all singing from the same hymn sheet on the issue of pay.

7

give information

[intransitive] informal to tell people everything you know about a crime when they ask you questions about it - used especially by criminals and the police:

I think he'll sing.

sing along 

phrasal verb

to sing with someone else who is already singing:

Sing along if you know the words.

sing along to

Jess was singing along to the radio.

sing out 

phrasal verb

1

sing out (something)

 to shout or sing some words clearly and loudly:

'Freeze!' a shrill voice sang out.

2 American English to sing loudly so that people can hear you easily

sing up 

phrasal verb

to sing more loudly:

Sing up, boys, I can't hear you!

Definition from the Longman Dictionary of Contemporary English
Advanced Learner's Dictionary.