Not content with producing bountiful 'regular' pedals, MXR has recently introduced limited-edition runs of exotic Custom Shop stompers. The latest in the CS line is a gnarly 70s-inspired octave fuzz. An octave button lets you punch the effect in and out, while output, tone and distortion knobs do the rest.
"Arpeggiated barre chords turn into self-imploding bursts of static"
If you're not familiar with octave fuzz, you've probably heard it on Jimi's solo in Purple Haze and the main riff to QOTSA's Little Sister. La Machine is a fine example, with a bright, ripping-Velcro texture that recalls the classic Foxx Tone Machine, and just begs for wide bends and colossal powerchords.
This being an analogue effect, playing anything other than single notes triggers some wild results: unison bends become pterodactyl screams, while arpeggiated barre chords turn into self-imploding bursts of static. At the lower end of the gain spectrum, you'll find ring mod-esque overtones, but upping the distortion knob a smidge returns you to crazy territory.
If you can bring yourself to turn the octave switch off, you'll find a thick, Muff-like fuzz that's just as menacing for riff workouts. This side of the pedal is a little dark, though, so you might struggle to get it to cut through in a live mix.