Sending keycodes to unfocused window (e.g. Spotify)

nofocusmm.sh

#!/bin/bash

KEY_NEXT=XF86AudioNext # keycode: 171
KEY_PLAY=XF86AudioPlay # keycode: 172
KEY_PREV=XF86AudioPrev # keycode: 173

# the window id of Spotify
SPOTIFY_WID=$(xdotool search --name "Spotify - Linux Preview")

if [[ -n ${SPOTIFY_WID} ]]; then
	# if Spotify instance is running send keycode to Spotify ...
	ACTIVE_WID=${SPOTIFY_WID}
else
	# ... otherwise send to active (focused) window
	ACTIVE_WID=$(xprop -root | awk '/_NET_ACTIVE_WINDOW\(WINDOW\)/ {print $NF}')
fi

case "${1}" in
	prev)
		xdotool key --window ${ACTIVE_WID} ${KEY_PREV};;
	next)
		xdotool key --window ${ACTIVE_WID} ${KEY_NEXT};;
	play)
		xdotool key --window ${ACTIVE_WID} ${KEY_PLAY};;
esac