sing out

verb

To cry out, e.g. when in pain.
““But I have known men sing out dreadfully when punished; if they had got enough of rum, it would have supported them, and they would not have sung out.” “Not one drop for me, Charley Hunter; I shall not sing out, I promise you, if they cut me to pieces”
““My lad,” said Captain Cuttle, “don’t you sing out afore you’re hurt.”
To call out; yell.
“The pilot would sing out, “Ready about ship,” and the seamen would return answer, “Ay, ay, Sir,”—again he would sing out, “All ready,” and would be answered with “All ready, Sir.””
“Vehemently pausing, he [Ahab] cried:—"What do ye do when ye see a whale, men?" "Sing out for him!" was the impulsive rejoinder from a score of clubbed voices.”
To call out to signal or advise of something, especially when prearranged.
“I'll be right outside. If you need anything, sing out.”
“Let's both search the house for my wallet. If you find it, sing out.”
To start singing.
“I’m gonna sing out: / I sing my song to the wide open spaces, / I sing my heart out to the infinite sea!”