If you are using a version of the AIY Project version aiyprojects-2017-09-11.img or newer you will have found that the mods I wrote to play radio no longer work.
The new version can be found at: https://github.com/ktinkerer/aiyprojects-raspbian/tree/voicekit/src
To play radio you need to the radio_mod.py and the vlc.py files, add these to your src folder. You also need vlc to be installed on the pi.
sudo apt-get update
sudo apt-get install vlc
The radio can be stopped by pressing the button, or by saying “radio off” (if the pi can hear you over the sound of the radio playing, I find this depends on the station you are listening to).