By heart

to learn something by heart

to know something by heart

He used to live in that town, and he still knows all the streets by heart.

You should play over all the pieces you know by heart at least once a month or oftener with the printed copies before you: or all sorts of wrong notes may creep in, and you will be leaving out some crescendo, or rallentando, or sforzato.

None of the other animals on the farm could get further than the letter A. It was also found that the stupider animals, such as the sheep, hens, and ducks, were unable to learn the Seven Commandments by heart.