Electro Harmonix Pico Swello

The Pico Swello builds on the legacy of EHX’s popular polyphonic effects, delivering expressive attack shaping and sweeping filter textures in a compact design. Its polyphonic attack filter applies envelopes to every note, single or chord, producing smooth swells, reverse-like textures, and synth-style tones that adapt to any style of playing.

Expressive Attack Control

The ATTACK knob is at the core, adjusting response from fast, subtle smoothing to long, dramatic swells. Used lightly, it creates a flowing feel even on quick runs. Pushed further, it transforms guitar into ambient washes or synth-like pads perfect for atmospheric soundscapes.

Low-Pass Filter Section

Activate the LPF with the Filter Button and shape the effect with three controls. FREQ sets the cutoff point, while MOD adjusts envelope depth and sweep direction for upward or downward filter movement. Resonance is selectable between low and high settings, adding flavor from subtle movement to pronounced peaks. The filter’s modulation timing is tied to the ATTACK setting, creating seamless interaction between the two.

Simple, Musical Layout

The four-knob design keeps operation intuitive. In addition to ATTACK and the filter section, VOL manages output to balance the naturally softer response of long attack times. Together, these controls unlock a wide spectrum of tones—from gentle smoothing to evolving textures—all with the musicality that defines EHX’s envelope-based effects.