sing off the same hymn sheet

cheat sheet

Any summary or quick reference used as a shortcut or reminder, such as an aid for public speaking.

dope sheet

A summary, ordinarily in the form of a document, containing important facts and background information concerning a person, activity, or other subject matter.

fast sheet

A hotel or similar establishment catering to prostitutes.

hot sheet

A list of items of high current interest.

silver sheet

By extension, movies, the film industry, or that which is related to movies or cinema (often preceded with "the")

sing a different tune

To hold a different opinion or appreciation (about something); to possess a new, changed, or regenerated mindset, usually for the better.

sing along

To sing some music while someone else is singing or playing the same piece of music or while it is being broadcast or performed

sing for one's supper

To work in exchange for some reward or recompense.