It is unusual for me to go to more than one concert in a night. Well, I often would like to, but it is generally not possible. But the same friends with whom I went to see PJ Harvey had bought tickets to Dean and Britta for the same night. It seemed possible to go to both, since PJH was at the Warner Theatre, while a mainstage show on Friday night at the Black Cat probably wouldn’t start until like 11. So we hopped in a cab from downtown and made it to the Black Cat while the opener was still fi…