jan 1, 1940 - flanger
A flanger sounds very similar to a phase shifter to the untrained ear, but it can have a much more drastically dramatic effect on your tone. Like a phaser, the signal is split in to two copies, then one of them is delayed in time slightly, usually no more than 20 millisecond. The delay time also changes at a constant rate, which can be manipulated with a knob.
Les Paul discovered the effect in the late 1940s and 1950s; however, he did most of his early phasing experiments with acetate disks on variable-speed record players. His 1955 single "Nuevo Laredo" features phase shifting, as does the 1953 single "Mammy's Boogie."
Flangers create a bigger, more complex harmonic reaction in the signal than a phaser, resulting in a more saturated and dramatic sound.
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unit 5 music technology in context