The Keeley Octa Psi Transfigurating Fuzz is a three-in-one pedal from Keeley Electronics that combines an all-analog fuzz with a polyphonic pitch shifter and octave generator. Released on September 24, 2024, it puts a high-gain, vintage Muff-style fuzz circuit and a DSP pitch-shifting engine in one box, with switchable effect order, momentary pitch ramping and an expression pedal input12.
Robert Keeley's original idea, which he dates to November 2021, was a high-gain vintage Muff, all-analog and all-transistor, feeding an octave pitch shifter, in the neighborhood of a Pitch Fork or POG2. The result is a pedal that can create intervals, subtle harmonizing, expansive octaves up and down, and swooping pitch bends, alongside a fuzz that Guitar Pedal X's reviewer described as "a very decent Big Muff voicing married to a most exceptionally accurately tracking Pitch-shifter"3.
A Muff-style fuzz and a pitch shifter in one box
The Octa Psi is a hybrid. The fuzz side is all-analog and transistor-based, with what Keeley describes as "wave after wave of gain staging leading to hard clipping" and a sound that "makes your guitar pickups sound enormous at any volume"1. The pitch-shifting side is digital DSP, offering a polyphonic pitch shifter, octave, fuzz and distortion effects in one unit1.
Robert Keeley told Premier Guitar that combining the two was the hard part2:
"It's very tough to combine a high-gain, full-analog distortion with a DSP [digital signal processing] section in one box."2
He also explained the fuzz voicing: because the pitch shifter can add an octave down, the fuzz was deliberately not voiced bass-heavy, but it still had to hold its own against any Big Muff2. The pedal covers several modes of octave up, octave down, and octave up-and-down fuzz voicings, including two octaves down6.
Pedal of the Day's reviewer summed up the concept when it launched:
"mixes distortion, fuzz, octave and pitch shifting together in some of the most unique ways we've ever seen"5
The controls
The Octa Psi has five knobs, two three-way toggle switches and a pair of footswitches, plus the rear expression input2. The pitch-shifter controls are marked in red and the fuzz controls in white, footswitches included, so you can tell the two engines apart at a glance6.
| Control | Section | What it does |
|---|---|---|
| Fuzz/Gain | Fuzz | Sets fuzz gain9 |
| Level | Fuzz | Adjusts output volume4 |
| Tone | Fuzz | Shapes the fuzz tone, interacts with the three-way tone switch4 |
| Low End EQ switch | Fuzz | Punch (bass boost), Psi (max undertones) or Scoop (scooped)19 |
| Blend | Pitch | Blends the shifted pitch with your dry signal7 |
| Pitch | Pitch | Sets the interval across a plus or minus two-octave range, including a detuned chorus effect67 |
| Up/Dual/Down switch | Pitch | Acts as a multiplier for the Pitch knob, for 24 total pitch combinations6 |
| Fuzz footswitch | Fuzz | Press-hold flips between latching and momentary ramping modes3 |
| Octave footswitch | Pitch | Press-hold with Blend sets ramp speed5 |
The three-way voice switch on the fuzz side delivers different bass responses, with Punch and Scoop options plus what Delicious Audio calls "the massive Psi mode"6. On the pitch side, the Up, Down and Dual modes cover nearly every harmonic interval, including power chords, stacked fourths and diminished chords1. The pitch shifter can run in momentary or latching mode, and its adjustable ramp speed allows creatively timed pitch bends, which Premier Guitar likens to having an onboard expression pedal1.
Preset modes save your settings in dual mode, and they are retained even after you unplug9.
Fuzz and pitch shifter order switching
The classic question with any octave fuzz is whether the octave comes before or after the fuzz. The Octa Psi answers it with instant order switching: hold down both the Octave and Fuzz footswitches at the same time and the signal path flips, so the fuzz feeds the pitch shifter or the pitch shifter feeds the fuzz125. Robert Keeley wanted order switching from the start, because the two routings give distinctly different sounds2.
Premier Guitar's news coverage put it simply:
"Instant Effect Order Switching: Solve the classic question 'Octave/Pitch before or after fuzz?' with ease, just hold down both foot switches."1
Power and connections
The Octa Psi runs on 9 to 18 VDC at 150mA from an external power supply, with no battery option; Keeley notes that a high-current power supply is sold separately1.
At 150mA the Octa Psi draws more current than a low-current daisy chain output can supply. Plan on a dedicated or high-current power supply output.
Connections are TS 1/4" jacks for input and output, and there is an expression control input on the rear18. Linking the Octa Psi with a standard expression pedal, in Premier Guitar's words, "opens the door to a whole new dimension of pitch shifting mayhem," though an expression pedal is not required2.
History and design
Robert Keeley began designing the Octa Psi in November 2021, and the finished pedal stayed true to that original idea2. In a 2025 Guitar World interview he said the development took real patience:
"It took three years before all of the different aspects came together."10
MusicRadar reported the pedal as over three years in the making and designed and built in the USA4. It launched on September 24, 2024 at an introductory price of $249673, and Guitar World confirmed the $249 street price the following day3. The pedal sits in a proprietary angled aluminum enclosure that Keeley chose for simplicity and durability1.
What reviewers made of it
Premier Guitar's review found the pitch shifter dependable under pressure:
"It tracks pitch changes well, and rarely collapses on itself, even when executing whole step bends colored by dissonant intervals."9
The same review noted that the manual contains an extensive pitch matrix, useful if you are finding your way by ear rather than working out the 24 pitch combinations yourself9.
Guitar Pedal X named the Octa Psi among its best new fuzz pedals of 2024, awarding it Bronze, third place, at $2493. The reviewer's verdict on the execution:
"Everything about this execution is top notch - and you're kind of getting a more expansive Big Muff here, combined with a sort of DigiTech Whammy."
"Everything about this execution is top notch, and you're kind of getting a more expansive Big Muff here."3
For players weighing it against other options in the octave and pitch lane, the Octa Psi's pitch shifter sits in the same neighborhood as the DigiTech Pitch Fork or an EHX POG, in Robert Keeley's own comparison, but with a Muff-style fuzz built in and routable either way around2. More on the category as a whole is on the octave and pitch pedals and fuzz pedals pages.
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Questions
Is the Keeley Octa Psi analog or digital?
It is a hybrid. The fuzz section is all-analog and transistor-based, with wave after wave of gain staging leading to hard clipping, while the pitch shifter and octave generator run on a digital DSP section. Keeley combined the two in one enclosure, which designer Robert Keeley described as a tough engineering problem.
Is the Keeley Octa Psi true bypass or buffered?
Both, and you choose. The Octa Psi ships with true bypass and silent buffered bypass as user-selectable options, so it can sit in just about any pedalboard setup. The fuzz footswitch can be press-held on power-up to flip between true and buffered bypass on the fuzz side.
Does the Octa Psi take a battery?
No. The Octa Psi runs on 9 to 18 VDC at 150mA from an external power supply, with no battery option. Keeley notes that a high-current power supply is sold separately, so a standard low-current daisy chain may not be up to the job.
What intervals can the Octa Psi pitch shifter make?
The Pitch knob covers a plus or minus two-octave range, and the three-way Up/Dual/Down switch acts as a multiplier, giving a total of 24 different pitch combinations. Modes include Up, Down and Dual for nearly every harmonic interval, including power chords, stacked fourths and diminished chords, plus a detuned chorus effect.
Sources (10)
- Keeley Introduces Octa Psi Pitch Shifter and Octave Fuzz, Premier Guitar, 2024-09-24
- Keeley's Mind-Blowing Octa Psi Pedal, Premier Guitar, 2024-09-24
- Guitar Pedal X, Guitar Pedal X, 2024-12-18
- “The ultimate combination of pitch-shifter, octave generator, and analogue fuzz!”: Over 3 years in the making, Keeley Electronics unveils the Octa Psi Transfigurating Fuzz, and it sounds wild, MusicRadar, 2024-09-24
- Keeley Electronics Octa Psi Transfigurating Fuzz, Pedal of the Day (www.pedal-of-the-day.com), 2024-09-24
- Keeley Octa PSI Transfigurating Fuzz, Delicious Audio, 2025-06-26
- “It has taken us a long time to get this package perfected. I've got everything in here that I could dream of”: Keeley spent three years crafting the Octa Psi, Guitar World, 2024-09-25
- OCTA PSI Transfigurating Fuzz! Keeley 3-in-1, gearnews.com, 2024-09-24
- Keeley Octa Psi Guitar Pedal Review, Premier Guitar, 2024-11-08
- Robert Keeley on the rise of Keeley Electronics, Guitar World, 2025-09-11
