sing out

verb4

1. •
   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.” — 1836
2. •
   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.
3. •
   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! — 1971
4. •
   To cry out, e.g. when in pain.

   • “My lad,” said Captain Cuttle, “don’t you sing out afore you’re hurt. — 1846