Free version here: https://play.google.com/store/apps/details?id=ch.pboos.android.SleepTimer
Unlocks the Free SleepTimer application. The free SleepTimer application needs to be installed.
Please try SleepTimer before buying to see if it works as you want. If the free version does not stop your music player, the paid version won't be able stop it either.
Additional features:- Widget- no ads