Sang or sung?

Sang is the past tense of Sing
Sung is the Past Participle of Sing. (used with the correct conjugation of HAVE)

The opera singer sang very well last night.
She has sung at the opera house many times.

yellow submarine was sung by whom?

GuestWhen should I use sang or sung?

The difference is the same as between knew and known, between took and taken, between gave and given, and so on.
Do you know your three principal parts of the verbs?
CJ

I sang the song, the song was sung by me.

George was the singer, he sang the song, the song was sung by George.

It sounded ok when I sang, it was better when George sang.

I love all the songs he has sung.

I especially loved the song he sang to finish.

When you use the passive voice like:
I sang the song. (active)
The song was sung by me. (passive)

In passive you use: Subject + form of to be + Past Participle

Is it, he didn't stutter when he sang, or He didn't stutter when he sung.

thank you very much your reply was useful

When referring to a piece of writing or poetry should it be, "These words were meant to be sung", or , "These words were meant to be sang"?

to be + past participle

to be sung