I have a Roland FP-7F and an old Art FX-1 Effects Processor. I wanted to connect them so I could play around with the effects. I play the piano just as a hobby and I don't really know what I'm doing. My one attempt to connect these failed.

I connected the left output from the piano to the left input on the FX-1 and the left output from the FX-1 to the left input on the piano. When I turned the piano on with the volume turned all the way down, I got a siren-like screeching from the speakers that kept getting louder. I immediately turned the piano off before I blew up something. I guess I created some type of loop?

Is it even possible to connect these two? I have a small Mackie mixer which I could add to the setup if that helps.

Any suggestions would be appreciated.

Roland FP7F
Korg Maxi-Korg
Roland Juno JX-3P
ARP Pro-Soloist