Why does music play on iphone 4s?

By a mistake i my iphone died of dead battery, so then i charged it up, now ringer and tones work, but when i go to play my music it say its playing but no sound is coming out of it? Why, i checked and volume is all way up but when i try to turn it down with the 2 buttons on side it does nothing, again why?
just trying to find out if somehow i locked it or something

Hold the power and home button until the device powers off and back on(basically until you see the apple logo again) you probably have to hold it for about 30 seconds

Go to settings, sounds, then make sure that under "ringer and alerts" the panel is set to OFF… Or maybe your earphones don't work, this happened to me so i just bought new earphones and i could hear again.