Live audio multiband compression

Hi, I would like to use a pi3 for a single task: to process live the stereo audio in signal with a multiband compressor and send it to audio out.

I would like to load and run this process every time it boots up and to run headless without attached monitor. Would be possible?

Surely , a few options away.
You can try with running a modep instance with some lv2 if you want a web ui .
If you dont mind about the ui you can use a lot of other options . Carla , jalv . Some run lv2 plugins on command line fashion so you dont even need the graphical desktop .

just need to create your preset , add the call to the program into the boot sequence of the pi and you are set .

But this being for live audio etc , its quite recommended to use PiSound since rpi 3 audio output from headphones etc its not amazing , and you dont get audio inputs . With a usb soundcard could be ok-ish for high buffer sizes , but PiSound its faster and higher specs