To its credit, the Lexicon 2400 was used by Stanley Kubrick in the making of Full Metal Jacket. Mr. Kubrick was compelled write an unsolicited thank-you note to Lexicon detailing one scene where it was used creatively; a scene where a rocket explodes into a building in slow motion. Other credits include the animations An American Tail and The Simpsons.
I designed all the algorithms for this unit including a pitch detector and a splicing algorithm. I designed the Splice board and Confidence board that together constituted the digital signal processing engine. The splicing algorithm had an entire board dedicated to its execution, as did the pitch detection algorithm: the Confidence board. I also designed the crystal oscillator that gave the unit timing accuracy to three decimal places (that design pushed TTL technology back then). [Jon Dattorro, Simple Techniques Extend Counter Range, Design Ideas, EDN magazine, pg.307, July 25, 1985] The unit also housed a host-board for user interface, and a machine-control board to interface with tape machines (designed by Manny Guerrero). Chuck Bagnaschi designed the beautiful front panel that made the unit very easy to use.
The splice engine comprised two TMS32010 DSP chips. The splice board queried the confidence board mathematical coprocessor. So there were a total of four DSP chips in this design. The splice board also performed digital filtering to compensate for aberrations caused by speeding or slowing tape machines of the type used by the television broadcast industry. The digital filters employed error feedback correction as discussed in my paper http://ccrma.stanford.edu/~dattorro/HiFi.pdf
The Lexicon 2400 has been reverse engineered many times; most notably by EvenTide Inc. Introduced in 1986, it remained in production through 1996. It also remains the standard for time compression in the United States and France. DILATATION ET TRANSPOSITION SOUS CONTRAINTES PERCEPTIVES DES SIGNAUX AUDIO by Gregory Pallone.