Donner EC966 Harmonic Square Octave Pedal with 7 Shift Types and True Bypass

Seven shift types and three tone modes give the Donner Harmonic Square a broad palette of pitch-shifted sounds in a compact pedal. Use it to explore octave, semitone, and detune effects, then shape the balance between the shifted signal and your original guitar tone with separate WET and DRY knobs.

The Sharp, Flat, and Detune modes make it easy to move between upward and downward pitch changes and a subtle detuned sound. For a layered part, you can keep some of the dry signal in the mix, for a more focused effect, adjust the harmonic level to suit the passage. What if one pedal could cover both a pronounced octave layer and a smaller pitch variation? The Harmonic Square’s 7 shift types and 3 modes provide 21 combinations to explore.

Worth noting

The Harmonic Square uses digital pitch shifting and features true bypass, so the signal can pass through a non-electronic bypass path when the effect is off. An LED indicator shows the pedal’s working state. Its aluminum-alloy construction and compact 3.7 x 1.7 x 2-inch dimensions make it a practical fit for a guitar setup where pedalboard space matters.

The separate WET and DRY controls are useful when you want the shifted notes to complement, rather than replace, the original sound. In a riff or single-note line, for example, adjust the wet level to bring in an octave layer while retaining the dry guitar signal. Customer feedback often highlights the range of sounds and clean low-octave tones, some buyers also report clicks when switching the pedal on or off.

Tips for day-to-day use

Set the WET knob to blend in the harmonic signal and use the DRY knob to adjust the original signal. Try Sharp for pitch-up sounds, Flat for pitch-down sounds, and Detune for an adjustable pitch shift of 10 cents. Working through the shift types with each mode is a straightforward way to find a sound for a specific part without changing instruments or relying on a separate pitch effect for every variation.

For power, use a 9V DC adapter with center-negative polarity and at least 500mA of current. The adapter is sold separately. The pedal connects through a 1/4-inch audio interface, making it suitable for adding pitch-shift options to a compatible instrument signal chain.

How to use it

Place the pedal in your instrument’s signal chain, choose one of the 7 shift types, and select Sharp, Flat, or Detune with the toggle. Use the WET and DRY knobs to balance the effect with the direct sound, then engage the pedal for the passage where you want the pitch change. This approach works well for adding a low octave to a guitar line, bringing a higher or lower pitch into a riff, or experimenting with detune for a different texture. The digital octave effect is also listed for guitar and bass use.

If you are choosing between a pedal focused on distortion and one designed for pitch changes, the Harmonic Square is built for the latter: its controls center on shifted pitch and the blend between wet and dry signals. That makes it a focused addition for players who want octave and pitch-shifter options rather than another gain effect.

Questions before you buy

What tones can the pedal create? It combines 7 shift types with Sharp, Flat, and Detune modes, for 21 combinations of octave, semitone, and detune sounds. Sharp shifts pitch up, Flat shifts it down, and Detune shifts the signal by 10 cents.

Can I balance the effect with my regular guitar signal? Yes. The WET knob adjusts the harmonic signal level, while the DRY knob adjusts the direct signal level.

What power supply should I use? Use a 9V DC adapter with center-negative polarity and a minimum current of 500mA. The adapter is not included.

Final verdict

The Donner Harmonic Square is a useful fit for guitarists and bassists who want several pitch-shifting options in one compact pedal. Its 21 mode-and-shift combinations, independent wet and dry controls, and true bypass make it especially suited to building octave layers, changing a riff’s pitch, and adding detune without giving up control of the original signal.