copy of his instrument being marketed at an American musical instrument trade show. He forced a legal settlement with Streetly Electronics. After visiting owners Frank, Norman, and Les Bradley in person (and having an intense discussion with Franson), an arrangement was made that Mellotrons would only be sold in the UK and Chamberlins would be sold in the US. Chamberlin would receive royalty payments from the Mellotron company, though this apparently ended in the late 1960s. Through this same royalty system, he licensed the Chamberlin "3 violins" sound to be used as the violins sound in the Mellotron library. This sound was used on much of the British Mellotron music since the mid-1960s. Consequently, it can be difficult to tell whether a recording features a Mellotron or Chamberlin when the three violins tapes are used, other than by the country of origin of the recording. Mistaking Chamberlin sounds for real instruments is common because they were recorded with no processing and because there were fewer mixdown master tapes used compared to the Mellotron library. The M series Chamberlins wide bandwidth playback heads also enhanced fidelity. Chamberlin instruments were never distributed for sale outside the US and Canada. Chamberlin Co. continued to refine and sell their products, and invested more effort into reliability to compete with the Mellotron. Sales to major US studios resulted in Chamberlins being heard on many pop records of the 1960s including recordings by The Lettermen, Marvin Gaye, Bobby Goldsboro ("Honey" in 1968), The Beach Boys, and educator Edmund Bordeaux Szekely. A new Chamberlin design emerged in the late 1960s, ending the use of rhythm tapes. This was the much more durable M1 which appeared in 1970 with a flawless tape-return roller system. This model has higher-quality playback tape heads with no tape warble and greater bandwidth than the Mellotron. The unit is a table-top version of the earlier models and much smaller than the competing M400 Mellotron model. About 130 M1 Chamberlins were built. These musicians included Disneyland/Disney Worlds' live performance artist Michael Iceberg in his shows featuring electronic instruments. Others include Skip Konte with Three Dog Night, Olivia Newton-John, Leon Russell (Carney in 1972), Neil Merryweather, James Taylor, Stevie Wonder, Ambrosia, Mike Pinder with The Moody Blues on the album Seventh Sojourn (1972), American progressive rock band Ethos, David Bowie (from Low in 1977 through Scary Monsters in 1980), Edgar Winter (Jasmine Nightdreams in 1975),