The Chamberlin instruments were designed to accurately replicate the sound of the instrument recorded on the tape. They were meant to be stationary and not transportable. so there was little effort devoted to reliability. Many early Chamberlins have no internal chassis and are prone to go out of adjustment. As Chamberlin refined the design he began to demonstrate it at music trade shows, and competitors such as Hammond and Lowrey were curious about the origin of Chamberlin sounds. In an effort to compete, these companies created drum rhythms and added plastic tabs with orchestral instrument names on them. These tabs would generate tones that simulated the sound of the instrument selected. The American Federation of Musicians took notice and attempted to limit live performances of Chamberlin instruments fearing that their members would be put out of work. Despite the controversy, musicians worldwide embraced the Chamberlin. "Mack the Knife" singer Bobby Darin was one of the first customers, buying a customized model 300 without the rhythm section tapes. Chamberlin's company grew by employing his children, and his window cleaner Bill Franson as his salesman. Franson travelled the country offering the Chamberlin instruments to music stores, parlours, and cocktail lounges. Offers of wider distribution were made, but Harry Chamberlin preferred word of mouth advertising and did not like the terms and conditions of distributorship and eschewed it. Chamberlin favoured doing business directly with lounges, nightclubs and musicians who embraced big band music. In 1962 Bill Franson went missing for several months. A radio could be heard playing music in his apartment but attempts to contact him proved futile. Franson had left for England by boat taking two Chamberlin 600 models with him (one of these eventually became the possession of Todd Rundgren's studio and appears on XTC's "Skylarking" album in 1986). Franson placed an ad asking for a company that could manufacture seventy standard playback heads. Bradmatic Ltd. (an engineering company) responded to the ad. Franson removed the Chamberlin labels and sold the rebadged "Franson" instrument without Harry Chamberlin's knowledge. Refining the 600's design into the Mellotron Mark 1, Bradmatic eventually became Streetly Electronics and began manufacture of the Mellotron Mark 2 in 1963. In 1965 Harry Chamberlin became aware of the fraud after being contacted by Mellotron distributors in America, and negotiated a 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.