How to delete all the music off my iPhone?

I synced my iPhone to iTunes on my computer. I've got a lot of songs in my iTunes library and my iPod has them all on it. When I synced my phone it randomly downloaded like 72 songs onto it, and I want to delete them all and start fresh. How do I do I delete them all (without altering my iTunes library)?

(Sorry I'm terrible with technology)

Go into settings:
General
Usage
Manage storage
Select the music app
Click edit
Tap the "delete" button next to "all songs"
Hope it helps! Cheers!

The same way it is that you delete other stuff on your phone.