Modulation and wah icons

Modulation and wah pedals add movement. A few designs from the '60s and '70s still define how these effects sound.

Wah

The wah is usually dated to 1966-67, when it was developed at Warwick Electronics/Thomas Organ for Vox, and the Dunlop Cry Baby carries that design on today. Rock the treadle and a filter sweeps from bassy to bright, like a voice saying "wah". Jimi Hendrix and Eric Clapton are commonly credited with making it famous. Vox still makes its own versions; side by side, the two are close cousins.

Phaser

The MXR Phase 90 has one knob: Speed. That simplicity is the point. It's commonly associated with Eddie Van Halen's early records, where it adds a subtle swirl to a crunchy amp. Try Speed around 10 o'clock for a slow, chewy sweep.

Chorus

The Boss CE-2 from the late '70s gave chorus its classic warm shimmer, a sound you'll hear all over '80s records. The Electro-Harmonix Small Clone is darker and more watery, with a Depth switch instead of a knob; it's commonly associated with Kurt Cobain.

Flanger

Flanging is chorus's jet-plane cousin. The Electro-Harmonix Electric Mistress is airy and metallic and is reportedly a favorite of David Gilmour and Andy Summers. The MXR Flanger is more dramatic, with deep, sweeping whooshes; it's commonly associated with Eddie Van Halen.

Uni-Vibe

Designed in Japan to imitate a rotating speaker, the Uni-Vibe throbs and pulses rather than sweeping smoothly. It's commonly associated with Jimi Hendrix's late-'60s performances and with Robin Trower. Many modern pedals copy its circuit.

Tremolo

Tremolo lived inside amps long before it moved into pedals. Fender amps of the '50s and '60s put it on the front panel, though Fender often labeled it "Vibrato", just as it called the whammy bar a "tremolo arm". Strictly, tremolo changes volume and vibrato changes pitch. Today's tremolo pedals copy that amp pulse, from soft and smooth to choppy.