what are the best octave pedals?
['Electro Harmonix Micro POG Polyphonic Octave Generator Guitar Effects Pedal.', 'Electro-Harmonix POG2 Polyphonic Octave Generator.', 'Electro-Harmonix Nano POG Polyphonic Octave Generator Pedal.', 'Electro-Harmonix Octavix Octave Fuzz Pedal.', 'Donner Digital Octave Guitar Effect Pedal.']