Phaser (effect) in the context of "Low-frequency oscillator"

An effects unit, effects processor, or effects pedal is an electronic device that alters the sound of a musical instrument or other audio source through audio signal processing.

Common effects include distortion/overdrive, often used with electric guitar in electric blues and rock music; dynamic effects such as volume pedals and compressors, which affect loudness; filters such as wah-wah pedals and graphic equalizers, which modify frequency ranges; modulation effects, such as chorus, flangers and phasers; pitch effects such as pitch shifters; and time effects, such as reverb and delay, which create echoing sounds and emulate the sound of different spaces.

In music, tape loops are loops of magnetic tape used to create repetitive, rhythmic musical patterns or dense layers of sound when played on a tape recorder. Originating in the 1940s with the work of Pierre Schaeffer, they were used among contemporary composers of 1950s and 1960s, such as Éliane Radigue, Steve Reich, Terry Riley, and Karlheinz Stockhausen, who used them to create phase patterns, rhythms, textures, and timbres. Popular music authors of 1960s and 1970s, particularly in psychedelic, progressive and ambient genres, used tape loops to accompany their music with innovative sound effects. In the 1980s, analog audio and tape loops with it gave way to digital audio and application of computers to generate and process sound.

Lester William Polsfuss (June 9, 1915 – August 12, 2009), known as Les Paul, was an American jazz, country, and blues guitarist, songwriter, luthier, and inventor. He was one of the pioneers of the solid-body electric guitar, and his prototype, called the Log, served as inspiration for the Gibson Les Paul. Paul taught himself how to play guitar, and while he is mainly known for jazz and popular music, he had an early career in country music. In the 1950s, he and his wife, singer and guitarist Mary Ford, made numerous recordings, selling millions of copies.

Paul is credited with many recording innovations. His early experiments with overdubbing (also known as sound on sound), delay effects such as tape delay, phasing, and multitrack recording were among the first to attract widespread attention. His licks, trills, chording sequences, fretting techniques, and timing set him apart from his contemporaries and inspired many guitarists of the present day.