Getty Images Fifty years old this month, Kraftwerk's single Radioactivity was a groundbreaking track that morphed into the German electronic pioneers' most political protest song. From the tremulous opening seconds of Kraftwerk's Radioactivity – a pulsing Geiger counter; escalating synths; shrill morse code spelling out the title – you sense that nothing will sound the same again. This core track from the German electronic pioneers' fifth studio album Radio-Activity (1975) feels like a scientific hymn, but it also strikes warning notes within its insistent hooks and haunting Sprechgesang (spoken singing) refrain: "Radioactivity / Is in the air for you and me".  Over the decades, Radioactivity itself has mutated, from elegiac melody to club banger and an anti-nuclear clarion call, while remaining fantastically distinctive. Half-a-century on, the album is reissued for its 50th anniversary, and this anthem still crackles with Kraftwerk's creative power.…