Pedals that stack with the Donner Harmonic Square Octave/Pitch Shifter

Walrus Audio EB-10

What Donner Harmonic Square Octave/Pitch Shifter brings here leans toward octave — that's worth building a pairing around

Xotic RC Booster

Xotic RC Booster leans toward transparent, and that's a real, usable character to pair with

Caroline Guitar Company Meteore

Put Caroline Guitar Company Meteore after Donner Harmonic Square Octave/Pitch Shifter in the signal chain, clear of Donner Harmonic Square Octave/Pitch Shifter's own gain stage — goes in the amp's FX loop (or last, into a clean amp)

Dunlop - MXR Carbon Copy Deluxe Analog Delay

Keep Donner Harmonic Square Octave/Pitch Shifter's octave voice out front: Dunlop - MXR Carbon Copy Deluxe Analog Delay goes after Donner Harmonic Square Octave/Pitch Shifter in the signal chain so its analog warmth voice doesn't muddy it — goes in the amp's FX loop (or last, into a clean amp)