<It is possible to make a pure analogue clean(ish) octave down circuit like the Electro-Harmonix Octave Multiplexer. These can only be monophonic and even the very best ones ever made can be “glitchy”, meaning that they don’t track perfectly and will jump between octaves. They tend to have a sweet spot and tend to work better with low notes. Being monophonic and working better with low notes makes these popular with bass players.>

not true, you can make a clean polyphonic analogue octave up or down circuit.

</If you want GLITCHLESS and CLEAN octave up and/or down, the only way to go is DIGITAL. The Electro-Harmonix Micro POG is a clean octave up/down machine. It is digital. The digital circuit allows algorithms that are smart enough to handle chords and make them sound good by preventing harmonic interference. The Micro POG only gives you octaves, but they are clean, they track perfectly, and they are POLYPHONIC.>

digital obviously makes things easier. but you can make a clean, polyphonic, octave up, down, or somewhere in-between pedal with analogue circuitry, it would just be extremely difficult to do, would recrquire a HUGE amount of electronics, and be expensive. But it is possible, especially with modern advances in analogue circuitry. (there is a push recently to make more advanced analogue circuitry that can do more things, because analogue circuitry can’t get hacked the way digital can.)