Guitar effects are electronic devices that modify the tone, pitch, or sound of an electric guitar, or condition or reroute the signal in some fashion. Effects can be housed in small effects pedals, guitar amplifiers, guitar amplifier simulation software, and in rackmount preamplifiers or processors. Electronic effects and signal processing form an important part of the electric guitar tone used in many genres, such as rock, pop, blues, and metal.Electric bass players use bass effects, which are designed to work with low-frequency tones of the bass.

The overdriven sound of distortion, which alters a signal’s waveform by “clipping” the signal, is an important part of an electric guitar’s sound in many genres, particularly for rock, hard rock, and metal. Filtering-related effects such as equalizers are used to adjust the frequency response in a number of different frequency bands, either for subtle sound shaping, to notch out unwanted resonance, or to enhance certain frequencies. Some filtering effects are used for creating more pronounced effects such as the “crying” sound of the wah pedal, the funky tone of the auto-wah, or the vocal-like sounds of the “Talk box. Volume-related effects such as volume pedals are used to adjust the volume of an instrument, make notes or chords fade in and out, or create a tremolo effect by rapidly increasing and decreasing the volume. A more complex volume-related effect is the compressor, which acts as an automatic volume control and smoothes out the peaks and valleys in the signal.

Time-based effects such as delay or echo pedals create a copy of an incoming sound which can be used for reverb effects; very long delay times can be used as a looping pedal. Modulation-related effects include the swirling sound of rotary speakers such as the Leslie speaker, the “whooshing” sound of the electronic Phase shifter, the psychedelic rock-style flanger, or the shimmering sound of a chorus effect. Pitch-related effects includes octave effects and pitch shifting pedals which can be used with an expression pedal to give a smooth bend-like effect or to add a parallel harmony part to a melody. Other pedals include switcher pedals; noise gates; and multi-effect pedals, which contain many different effects in a single chassis.