In the mid-60s, US soul singer James Brown developed a new style of music called funk. In soul music the melody and lyrics are central, but in funk the rhythmic groove is central. A funk groove can continue for a long time without chord changes, and funk songs in the 60s often lasted for ten minutes or more. By the early 70s, nightclubs called discos were employing DJs to play dance tracks because it was cheaper than hiring a band. At first they played funk and up-tempo soul tracks, but in the mid-70s they started playing tracks with a new rhythm that was easier to dance to. Another new genre of dance music called techno developed in Detroit in the early 80s when club DJs began making electronic dance tracks. They used drum machines to create electronic rhythms and synthesizers with keyboards to add chords and melodies. Another style that developed in the 90s is drum and bass (or "DnB"). Most DnB has very deep bass sounds, jazzy breakbeat rhythms, and is very fast and a...