Note: The following history was compiled through various sources over a long period of observation. Most of the exact dates and pivotal occurences are paraphrased from Forrest White's excellent book "Fender, The Inside Story" (GPI Books, Miller Freeman Publishing).
I cannot otherwise verify some of these facts and would appreciate any additional information ...factual or anecdotal... from those who were actually there.
In 1971, Leo Fender, Forrest White and Tom Walker formed a new musical instrument company they called "Tri-Sonics, Inc.". Leo and Tom started to layout the scheme for the amplifiers while Forrest worked on a new design for their guitars and bases that would not be confused with the Fender instruments.
By 1973, the company name had been changed to "Musitek, Inc." (short for "Music Technology"). By January, 1974 the company underwent their final name change to "Music Man". All during this time, Leo Fender was being cautious not to take an active roll in the company because his 10-year "non-compete" clause with CBS (due to the sale of Fender Musical Instrument Company to CBS in 1965) hadn't yet legally expired. In 1975 Leo came out from behind the curtain and announced he had been elected president of Music Man, Inc.
In 1974, production of the amplifiers had started. These were the earliest versions of the "Sixty Five" series with the 12AX7 phase splitter and a pair of Sylvania 6CA7 output tubes. Production of these amps as well as their 130-watt bretheren continued into 1979 with few changes (except for the change to a solid-state phase splitter design). In August of 1979, Leo's wife of 45 years, Esther, passed away after a long illness. Esther was no doubt the "woman behind the man" that created the Fender music legend.
New models were introduced in late 1979 into 1980, mainly upgrades to the power output, the addition of the RD (Reverb/Distortion) and RP (Reverb/Phasor) models and a new corporate identity which consisted mainly of reversing the color scheme of the logo plates!
Throughout the early 80's, new models (including the smallest amps such as the RD/RP50 and the uprated RD/RP100 series) and cosmetics continued to be introduced. It was during this time period that the rare white tolex and white "pinwhal" (a sort of vinyl cordouroy) coverings were introduced. By 1982 the writing was on the wall, and Leo Fender formed his new guitar company... G&L guitars.
Due to internal mismanagement and ownership squabbles, the company went downhill financially. After considering several offers, Music Man was sold to Ernie Ball on March 7, 1984. Music Man's remaining physical assets were sold on June 1, 1984. A sad end to an amazing decade in musical instrument amplifiers!