I did intend to run both pikaraoke and modep at the same time. And I got it working eventually 
First thing was to re-flash Patchbox OS and run the wizard and select the desktop auto login environment. Then I ran apt update and inatalled pikaraoke as per the instructions. I then ran it NOT using sudo and made sure to set the download folder to ~/pikaraoke-songs
This got it to run so I connected to it using my phone and started a song. No sound out of pisound but out of the headphone jack. So I shut the pi down and rebooted and on the second try the audio came out of the pisound. Winner
So next I installed modep, then installed the lv2 modules as per instructions here [Plugins] Only 73 plugins available in modep - #6 by Pranciskus which removed python3-pygame so I uninstalled the plugin which removed it and re-installed pygame.
Then after another reboot I plugged in the mic and connected to modep, added a reverb and that worked on the mic. Running pikaraoke stlll worked so I was able to sing on top of the backing with effects applied. Awesome sauce