represented by the linear prediction filter. This restriction is the primary reason that LP coding is almost always used in tandem with other methods in high-compression voice coders. Waveform-interpolative Waveform-interpolative (WI) vocoder was developed in AT&T Bell Laboratories around 1995 by W.B. Kleijn, and subsequently, a low- complexity version was developed by AT&T for the DoD secure vocoder competition. Notable enhancements to the WI coder were made at the University of California, Santa Barbara. AT&T holds the core patents related to WI, and other institutes hold additional patents. Artistic effects Uses in music For musical applications, a source of musical sounds is used as the carrier, instead of extracting the fundamental frequency. For instance, one could use the sound of a synthesizer as the input to the filter bank, a technique that became popular in the 1970s. History Werner Meyer-Eppler, a German scientist with a special interest in electronic voice synthesis, published a thesis in 1948 on electronic music and speech synthesis from the viewpoint of sound synthesis. Later he was instrumental in the founding of the Studio for Electronic Music of WDR in Cologne, in 1951. One of the first attempts to use a vocoder in creating music was the "Siemens Synthesizer" at the Siemens Studio for Electronic Music, developed between 1956 and 1959. In 1968, Robert Moog developed one of the first solid-state musical vocoders for the electronic music studio of the University at Buffalo. In 1968, Bruce Haack built a prototype vocoder, named Farad after Michael Faraday. It was first featured on "The Electronic Record For Children" released in 1969 and then on his rock album The Electric Lucifer released in 1970. In 1970, Wendy Carlos and Robert Moog built another musical vocoder, a ten-band device inspired by the vocoder designs of Homer Dudley. It was originally called a spectrum encoder-decoder and later referred to simply as a vocoder. The carrier signal came from a Moog modular synthesizer, and the modulator from a microphone input. The output of the ten-band vocoder was fairly intelligible but relied on specially articulated speech. Some vocoders use a high-pass filter to let some sibilance through from the microphone; this ruins the device for its original speech-coding application, but it makes the talking synthesizer effect much more intelligible. In 1972, Isao Tomita's first electronic music album Electric Samurai: Switched on Rock was an early attempt at applying speech synthesis technique in electronic