execute_on_song_change = "ncmpcpp --now-playing > ~/.psi/tune"This line executes ncmpcpp (recursion!) when song changed.
This way have a issue: ncmpcpp --now-playing not give newline. It not show a user tune according XEP-0118.
If you want to match the standard, you should to install MPC and you fix the line:
execute_on_song_change = "mpc --format '%title%\n%artist%\n%album%\n%track%\n%time%' | head -n -2 > ~/.psi/tune"
If the instructions do not help, you may check:
*It works only if ncmpcpp run.
*ncmpcpp not have hook for pause or stop.