Default 'Ok Google' spontaneous open when using Google Music All access

Hi,

Recently started the trial of Google play music all access.


I have the Google Now apps installed so My Moto G has the full 'OK Google' functionality going on.

For some reason, the phone 'beeps' and opens up voice search for no reason 80% of the time when a new track starts, or if I skip a track.

Does anyone know why this is, This is usually when a quiet instrumental is playing at the beginning of a song so It's not being driven by someone saying 'ok google' in the song ..

Any thoughts whats going on. I don't want to disable voice because its actaully very useful when driving to control google maps, etc.

cheers