A girl group is a music act featuring several female singers who generally harmonize together.The term "girl group" is also used in a narrower sense within English-speaking countries to denote the wave of American female pop singing groups who flourished in the late 1950s and early 1960s between the decline of early rock and roll and the British Invasion, many of whom were influenced by doo-wop style.All-female bands, in which members also play instruments, are usually considered a separate phenomenon.