Flangers, phasers and choruses are from a family of effects called modulation effects. These effects work by creating a series of frequency notches that are slowly swept across the frequency spectrum (hence modulation). Because the notches result in frequency attenuation you don’t really ‘hear’ the notching but you hear the frequencies that are not affected by the notching.
Phasing is the subtlest of these effects and is the result of a small number of evenly spaced notches in the frequency spectrum. Flanging and chorusing are distinct from phasing because they both double and delay the input signal which results in frequency notches that are spaced harmonically across the frequency spectrum. As a rule of thumb, flanging is the result of delay times less than 1ms to 5ms while chorusing is the result of delay times between 5ms and 25ms.
Flanging is considered the most dramatic of these effects and is sometimes described as being inside a drainpipe, a swooshing sound or an airplane taking off. It was first conceived in the late 40s of 50s by Les Paul but didn’t receive widespread adoption until it was use on “Itchycoo Park” by The Small Faces (1967). Flanging became popular overnight and was used by the likes of The Beatles and Jimi Hendrix. In the 60s, achieving a flange effect was not as simple as loading up a flanger on your track. The workflow was expensive and laborious. It involved recording the performance onto two different tapes. The tapes were then played back in sync while the output was recorded onto a third tape machine. While the two original tapes were played, the engineer would slow the playback of one of the tapes by gently pressing a finger on the metal rim of the playout reel that is called a flange. This would cause an audible sweeping sound as the tapes went out of sync. To bring the sweep back in the other direction the engineer would slow the playback of the other tape to bring the tapes back in sync.
Although Live has a built in Flanger you can make one yourself by following the steps in the video below. Try using flangers in a subtle way (low Dry/Wet %) on all kinds of instruments to add life. Try adding flange effects on the mid/high range of your basses, on your ride cymbals, drums fills and strings. Another way to add ‘soft’ flanging creatively is to use it as an insert effect before a reverb or delay. Try experimenting with a flanger before a distortion effect to add girth and interest to the sound.