However, acts that were successful within Australia rarely managed to achieve any lasting success overseas, generally due to the combination of poor management, lack of record company support or lack of radio exposure. The era also saw the popularity of local versions of rock musicals and festivals. Early "Third wave" Until the late 1970s, many Australian rock performers found it hard to become established and to maintain their profile, because of the difficulty in getting radio airplay. Until 1975, Australian mainstream radio was dominated by a clique of commercial broadcasters who virtually had the field to themselves and their influence over government was such that no new radio licences had been issued in any Australian capital city since the early 1930s. All commercial radio was broadcast on the AM band, in mono, and that sector strenuously resisted calls to grant new licences, introduce community broadcasting or open up the FM band (then only used for TV broadcasts) even though FM rock radio was already well-established in the US. Many of the more progressively-oriented artists found themselves locked out of these radio stations, which concentrated on high-rotation of a small list of three-minute pop singles. This was a result of the widespread adoption of the US-inspired "More Music" format. A conflict between radio broadcasters and record labels resulted in the 1970 radio ban from May to October. During the ban major UK and Australian releases were refused airplay on commercial radio—but not on Australian Broadcasting Commission stations. A series of cover versions of UK singles by local artists on new labels, including Fable Records, were commercially successful. This is exemplified by Liv Maessen's version of "Knock, Knock Who's There?", which reached No. 2 on Go-Sets National Top 40. However the original version by Mary Hopkin was not well known to contemporary listeners. After the ban even though there was a great deal of innovative and exciting music created by Australians; few listeners heard more than a fraction of it. By the 2000s their music underwent a resurgence of interest, both locally and internationally, as the country was one of the last untapped sources of 20th-century rock music. Popular rock music acts of this period include Spectrum and its successor Ariel, Daddy Cool, Blackfeather, The Flying Circus, Tully, Tamam Shud, Russell Morris, Jeff St John & Copperwine, Chain, Billy Thorpe & the Aztecs, Headband, Company Caine, Kahvas Jute, Country Radio, Max Merritt