Four of progressive rock's most successful bands – King Crimson, Yes, ELP and Genesis – went on hiatus or experienced major personnel changes during the mid-1970s. Macan notes the September 1974 breakup of King Crimson as particularly significant, calling it the point when "all English bands in the genre should have ceased to exist". More of the major bands, including Van der Graaf Generator, Gentle Giant and U.K., dissolved between 1978 and 1980. Many bands had by the mid-1970s reached the limit of how far they could experiment in a rock context, and fans had wearied of the extended, epic compositions. The sounds of the Hammond, Minimoog and Mellotron had been thoroughly explored, and their use became clichéd. Those bands who continued to record often simplified their sound, and the genre fragmented from the late 1970s onwards. In Robert Fripp's opinion, once "progressive rock" ceased to cover new ground – becoming a set of conventions to be repeated and imitated – the genre's premise had ceased to be "progressive".