The signature Kraftwerk sound combines driving, repetitive electronically-generated rhythms with catchy synthesizer-generated melodies, mainly following a Western classical style of harmony, in a minimalistic arrangement. The group's simplified lyrics are at times sung through a vocoder or generated by computer-speech software. In the early to late 1970s and the early 1980s, Kraftwerk's distinctive sound was revolutionary for its time, and it has had a lasting impact across nearly all genres of modern popular music, especially on electronic music.