Eli Gerstner and The Chevra Sing Acapella does not sound like an acapella do-wop group, a Jewish vocal group like Beatachon or a barbershop quartet. They mainly have one guy singing while the other three guys sing back-up with light "ooh ooh". There is one exception on the album where they have a more four-part harmony sound with "da dum da dum". The album sounds more like vocal versions of their other albums, which is to say, sort of pop style vocals. All the songs are composed by the well-known Rabbi Shlomo Carlebach. Although there are some slight variations, the melodies should be familiar to Carlebach fans.
The album was released in 2002 making it the follow up to their hit debut album which introduced the Jewish music world to the now prolific Eli Gerstner and a different kind of Jewish singing group. The Chevra is kind of like Mordechai Ben David and Avraham Fried, but there are four of them and the beats and rhythms are a little more pop and a little less cantorial based. At least that's how I hear it.
Once I interviewed hasidic singer Udi Ullmann and he said he saw a huge difference between popular Jewish music in England and in America. He said in America the groups were mostly group like The Chevra and in England it was mostly a single singer.
One of my favorite songs of all time is The Chevra's Shema Hashem from their first album. It starts out acapella and then moves into this driving beat.
You can get The Chevra's acapella album here.