I haven’t tried it with bass, but the Pitchfork is digital and polyphonic, so it shouldn’t have any problem tracking a bass.

I like it when bass plays chords under a lead guitar. I also like octave bass, up or down, but I don’t get straight parallel thirds or fourths. I think diatonic intervals are more useful, but you don’t get those with straight pitch mod machines. You need an effect that knows what key you’re in.

For a really good octave down ONLY sound, you can use the EHX Octave Multiplexer. It’s not listed as a bass effect, but I’m pretty sure it will work with bass, at least the original that I had many years ago did. The Octave Multiplexer is 100% Analogue and it is monophonic, so it will get confused if you throw intervals or chords at it.

The Bass Micro Synthesizer has the same circuit as the Octave Multiplexer for the Sub Octave channel. It also gives you an Octavix ( Octavia-like ) octave up, that means it’s distorted, and a square wave which is just a super clipped signal, basically a distortion. The filters on the Bass Micro Synth are tweaked for bass frequencies. This is also a 100% analogue effect which makes it essentially monophonic when you’re using the octave channels.

Again, if you only need an octave, the POG series is digital and polyphonic and it can give you a pure octave up and/or octave down. Even though it only does octaves, some people prefer the tone and ease of use of the POG to the Pitchfork in side-by-side comparisons. I’ve never seen a POG-Pitchfork shootout using a bass, so it might be that one tracks bass better than the other.