Following the artistic and commercial breakthrough of Autobahn, 1975's Radio-Activity found Kraftwerk consolidating the strengths they had begun displaying on the earlier album. All traces of their flute-playing, longhaired hippie past were eradicated as Kraftwerk fully embraced an all-electronic sound. It was their first album to feature the two-man electronic percussion team of Karl Bartos and Wolfgang Flur; hence the increasing reliance on rhythm. And it was the band's most vocal-oriented, pop-friendly album to date, expanding on the accessibility of their first hit single, "Autobahn." The conceptual thread of radio transmission was part of a growing obsession with technological themes, just as the group's commitment to electronic gear was becoming greater than ever.