A Partial History Of The Selmer Varitone:

In 1965, H & A Selmer, Inc. began to develop one of the most radical concepts ever envisioned: an 'electric' saxophone. The company called on Electro-Voice (EV) to assist them in the electronic portions of the product. Initially, the saxophone was meant to have a built-in means of amplification so acoustic feedback was not such an issue. What developed was considerably more complex than a simple amplifier. Through conversations with players, and heavy development on the part of both companies, the resulting product was a radical shift in the tonal concept of the saxophone. With this unit installed, a musician had complete control over their output volume and tone quality, and even more amazing was the ability to add echo, tremolo and a concurrent sub-octave synthesized tone.

By Jason DuMars

For the full history, see the source on saxophone.org.