Just to be sure credit is given where credit is due, this is a port of Fonz Adriaensen's ambisonic reverb (Zita-Rev1). The brilliant piece of work is due to Fonz, who is the person that understands this stuff. I can only take credit for rehashing to get it to compile on Bela, and the _mono function to extract what I wanted when processing a single channel.
The fundamental algorithm that Fonz implemented is very flexible and is easy to get nice sounds from it. I have used the original plugin application as Fonz coded it on my Debian machine running on JACK, so I knew it was worth my time porting the code to Bela. In either case I agree, it's a brilliant piece of work for which I can't take credit 😃