Since i3 is a keyboard driven windows tiling manager it comes to no surprise that the keyboard shortcuts are mentioned in the config file.

# audio  like Spotify

bindsym XF86AudioRaiseVolume exec "amixer -D pulse sset Master '5%+'"
bindsym XF86AudioLowerVolume exec "amixer -D pulse sset Master '5%-'"
bindsym XF86AudioMute exec "amixer -D pulse set Master toggle"
bindsym XF86AudioPlay exec "dbus-send --print-reply --dest=org.mpris.MediaPlayer2.spotify /org/mpris/MediaPlayer2 org.mpris.MediaPlayer2.Player.PlayPause" 
bindsym XF86AudioNext exec "dbus-send --print-reply --dest=org.mpris.MediaPlayer2.spotify /org/mpris/MediaPlayer2 org.mpris.MediaPlayer2.Player.Next" 
bindsym XF86AudioPrev exec "dbus-send --print-reply --dest=org.mpris.MediaPlayer2.spotify /org/mpris/MediaPlayer2 org.mpris.MediaPlayer2.Player.Previous"
bindsym XF86AudioStop exec "dbus-send --print-reply --dest=org.mpris.MediaPlayer2.spotify /org/mpris/MediaPlayer2 org.mpris.MediaPlayer2.Player.Stop"

These are all the buttons ‘some’ of the keyboards have volume +, volume -, mute volume, play, next, previous, stop.

If anything is not working, may be you should go looking for a different command for your device or distro.