1
general::
Call out loudly, shout, as in One of them fell in the stream and sang out for help. [Early 1800s]
American Heritage Idioms
2
general::
Phrase(s): sing something out
to sing or announce something loudly. • The teacher sang the names out loud and clear. • She sang out "The Star-Spangled Banner" in a loud voice., Phrase(s): sing out
to sing louder. • Sing out, please. This is a very large hall. • The sopranos will have to sing out more.
McGrawhill's American Idioms And Phrasal Verbs