My iPhone just randomly turned off whilst in the midst of playing music, it won't turn back on and I've tried holding the sleep/wake button whilst holding the home button and still NOTHING.. Please HELPP!!!x

my iphone 4 just randomly turned off whilst I was playing music. It wont turn back on. Ive plugged it into the computer and tried to charge it but nothing is happening. I have also tried this rest thing and it's not working. but I'm wondering if i was doing it right.. I was holding the power button at the top of my phone whilst pressing the home button (???) HELP ME PLEASE! x