How to make phone play a custom sound after pressing physical button? I have LG G2 Mini with Lollipop. 

In Settings there is an option that allows the phone to quickly launch apps at the locked screen. So when you press and hold volume down it can open the Camera, and with volume up it can run QuickNote. 

I want to replace this volume up gesture. Instead of running QuickNote I want it to play a custom sound.
OK, I found an answer by myself :-) To add action to volume button I used Key Plus app (https://play.google.com/store/apps/details?id=com.apptuners.keyplusapp). Then I created a task with Tasker (https://play.google.com/store/apps/details?id=net.dinglisch.android.taskerm&amp;hl=pl) which set media volume to max, play a sound, wait till it ends and revert volume to previous value: