To Enable/disable Music or Sound Effects in the game. you will have to go to Settings. To do so, tap on the cog icon on the left upper corner of your screen.
When selected, you will see the sound and music options arranged vertically, represented by the megaphone and quaver icons respectively. Keep in mind that if the option is activated, the toggle will be towards the right in green color, and when you disable it, it will be placed towards the left.