Macbook Pro beeping on startup

Your Mac makes a distinctive, multi-tonal "chime" sound when it passes the Power on self test. Repeating that chime sound is a much different problem from other, simple tones used for error outputs at Startup.

¿which are you hearing?

If you can get it to boot, try resetting the NVRAM. As soon as the screen comes on, or you hear the startup sound, hold in Shift+Command+P+R. Keep holding them in until you hear the startup sound again.

If that didn't help, there may be a faulty memory. If it's a Unibody machine (not a Retina) you can remove and replace the memory yourself. Try starting it up with only one memory stick in the slot closest to the bottom of the machine, then try with the other stick. If you decide to buy new memory, make sure it's Apple compatible memory. Macs aren't very happy with anything else.