YOU SAID:

My mom used to sing at bars.

INTO JAPANESE

私の母はよくバーで歌っていました。

BACK INTO ENGLISH

My mother used to sing in bars.

INTO JAPANESE

母はバーで歌っていた。

BACK INTO ENGLISH

My mother was singing in the bar.

INTO JAPANESE

母はバーで歌っていた。

BACK INTO ENGLISH

My mother was singing in the bar.