… I need to “open” the harmonizer only on specific notes or phrases, often with quick changes … Is there a way to activate/deactivate the bypass or the output quickly and temporarily and perhaps with a button that I can handle with the heel of my foot? …
You have several options. The most versatile way is mapping an auxiliary switch to the expression pedal settings. Joe Cozzi explains the process more succinctly than I have. [link below – around 3:00 and 5:00 minutes in]. It’s H9 / HotSwitch-focused, but the same applies to the PF. This is the method I often use to momentarily change Key / Scale or harmony intervals on-the-fly.
Also, you can directly assign Bypass, or the function of one of the three physical switches. In all of the PitchFactor algorithms, ‘Parameter 1’ controls MIX. So you can snap between a MIN / MAX range of dry to wet. Caveat: that will be a Global assignment, while the EXP PED methods above can be tailored per-preset.
Your external switch … it can be most any momentary. Something sturdy. A few Boss FS-6’s each give me TIP, RING, TIP+RING, plus momentary / latching & polarity toggles. Any common keyboard sustain switch has a great feel to it, for a single [TIP] assignment.
I am assuming you’re not using MIDI, but there’s a superset of the AUX Switch functions to be found there. I don’t play brass / woodwinds, but I admire your spirit of exploration. I’d guess that – in General Settings: Source Instrument – it might be worth trying out SynthLead & SynthBass. My personal preference: I use a Bypass Mode of DSP+FX. I find that RELAY or DSP make the transitions a little too abrupt.