# in .tmux.conf
bind-key -T prefix F1 run-shell "mpec t >/dev/null"
bind-key -T prefix F2 run-shell "mpec p >/dev/null"
bind-key -T prefix F3 run-shell "mpec n >/dev/null"

# in ~/bin/mpec
#!/bin/ksh

case $1 in
 p) mpc prev &;;
 n) mpc next &;;
 t) mpc toggle &;;
esac

return 0

# C-b F1 toggles playback
# C-b F2 plays previous song
# C-b F3 plays next song