How to reown a process?

Question

when i run this script with a shortcut(sxhkd):

#!/bin/sh

MUSIC_DIR="$HOME/music"

songs=$(ls "$MUSIC_DIR")

filename=$( echo -e "random\n$songs" | dmenu -l 30 -i -p "Play >> ")

if [[ $filename = "random" ]]
then
    filename=$(ls "$MUSIC_DIR" |shuf -n 1)
fi

if [[ -f "$MUSIC_DIR/$filename" ]]
then
    notify-send -t 2500 "$filename is playing" &&  mpv "$MUSIC_DIR/$filename" --no-audio-display
else
    notify-send -t 1500 "typo?"
fi

I want to open a terminal control mpv process on it ( get the mpv terminal interface ).

I have tried reptyr, but I'm getting this error.

~ λ  reptyr $(pgrep mpv)
[-] Process 514610 (dmenuMusic) shares 514636's process group. Unable to attach.
(This most commonly means that 514636 has sub-processes).
Unable to attach to pid 514636: Invalid argument

also tried:

~ λ  echo 0 | doas tee /proc/sys/kernel/yama/ptrace_scope

It just didn't work, gave me same error.