How can I mute music and sounds while playing?

The app starts up with background music etc., and this isn't always a good idea to have on - how can I mute the game volume, without having to do so for all apps?

Tap the Pokeball at the bottom of your screen.

From there, tap Settings in the top right corner.

Once you're in the Settings menu, you can disable sounds using their appropriate checkboxes:

The red & white small pokeball icon in the bottom middle of the screen calls up a menu screen with various options such as Pokedex. On that screen, there is a further 'Settings' menu on the top right - which has the options to mute sound effects and music.