Hawkwind are an English rock band, one of the earliest space rock groups. Their lyrics favour urban and science fiction themes. They are also a noted precursor to punk rock and now are considered a link between the hippie and punk cultures. Formed in November 1969 by singer-songwriter and guitarist Dave Brock, Hawkwind have gone through many incarnations and styles of music. Critic Jim Green describes their trademark sound as characterised by "that gargantuan and impenetrable pre-metal/hardcore drone, those great riffs, that inexorable drive to destinations unknown". Dozens of musicians have worked with the group; fantasy and science fiction writer Michael Moorcock was an occasional collaborator.