External Audio Envelope Technique Question

I was running external audio through the Super 6 today, and I had difficulty utilizing Envelope 1 on material with long decay times (think piano or Rhodes). It seems like there are two ways to pass audio through the synth:

Poly 1: Opens a gate once the audio reaches a certain threshold. This triggers Envelope 1 and the LFOs (awesome!), but the sound cuts in and out in a glitchy way once the audio tails pass below the threshold. Increasing the gain introduces distortion and doesn’t solve the problem, as the tails get quite soft.

Poly 2: A key press opens the gate, allowing the audio to pass through with the tails intact (great!). But, Envelope 1 isn’t triggered, leaving me out in the cold if I’d like to use it as a mod source.

Possible (but annoying) workaround: I can use Poly 2 and first press (and hold) a key to open the gate. I can press other keys whenever I want Envelope 1 to open. MIDI programming makes this kind of do-able, but it would take real time to get together. I’m a wind player, and the thought of transcribing my own solos into MIDI seems cumbersome.

My question: Is there a way to open the gate and keep it open to preserve audio tails, while engaging Envelope 1 above a given threshold? Or another solution? Feel free to correct me if I’m misunderstanding any of these concepts. Thanks!