Every bar is treated differently. Usually a month 1000 or so, it seems to be from 7 pm to 12 pm. If there are fewer guests, it can be earlier.
Generally speaking, the boss will ask you to prepare a few songs and try to sing them. You think it's ok, but you also need to be able to talk and give the boss the feeling that you will take care of the bar like a master, so it's ok! Prepare 1 and 2 English songs. . . good luck