Traditional Jewish worship requires a minyan (a quorum of ten adult males) to take place.
In an Orthodox synagogue the service will be conducted in ancient Hebrew, and the singing will be unaccompanied.
Few British synagogues now have a choir, but they are more common in the USA.
In a progressive (Reform, Liberal) synagogue the service will be at least partly in English, there may a choir and instruments, and men and women can sit together.