 DATE: When Marty completes the improvised guitar ending for "Johnny  B. Goode," he kicks over the guitar amplifier. The amplifier makes  the electronic "splash" sound like a guitar amplifier that has a  reverb tank. Guitarist Dick Dale (I) (qv) and Leo Fender developed  the first prototype reverb unit in 1961. Fenders Fender Musical  Instruments Corp. introduced the first reverb units in 1962, seven  years after the dance, which takes place in 1955.