Drop in External Audio Effect. Assign Mod Wheel to 'Audio From' Gain (inf - 0.00)
Set Audio From as your sound source (maybe mic?) leave Audio to as none. Keep mod wheel down to avoid feedback.
Drop in Looper. Set Quantize and Song and Tempo Controls to None.
Assign Speed knob on Looper to C1 - C3 on your keyboard (or equivalent. Two octave range, middle C will be center). Set the range as -12 to 12.
Possibly assign the main button to a nearby key as well. (I have C#3).
Drop in Gate effect. Set Audio From in sidechain to the channel your Looper is on, change level beneath Threshold from -40 to -inf. Turn on Sidechain. Maybe lower the Threshold a bit.
Tricky part:
Place an audio clip on that channel in session view. Make sure the audio clip has a consistent, loud tone throughout (sine or noise or something).
Turn on warp and Loop (I'm using complex).
Change Launch settings on clip. Launch Mode set to Gate, Legato on, Quantization to None.
Midi map the clip to the same key range as the Speed knob of Looper (C1-C3).
Now set mod wheel to appropriate level (unless you want fade-in) and trigger looper while making sound (mostly only works well for long ambient noises and tones). Retrigger Looper so that it loops the material. If overdub is on you always have the option of adding more material using the mod wheel. You can even add sound As you play a key!
Unfortunately it is glitchy and monophonic. Fun still
