What is "mu-tron"

Musitronics, often shortened to Mu-tron, was a manufacturer of electronic musical effects active in the 1970s. Founded by Mike Beigel and Aaron Newman, the company's product line focused on filtering and processing effects derived from synthesizer components. The company was known for producing high-quality products with many user-adjustable parameters, but high production costs and a failed product line, the Gizmotron, caused its downfall.

Their best-known product was the Mu-tron III envelope filter, "the world's first envelope-controlled filter", first made in 1972 and quickly becoming an essential effect for many funk musicians. It was taken in production again, in a modified version, in 2014.