Please allow users a default option to hear quick play demos tracks WITHOUT vocals.
You can remove the demos with vocals and replace them with one without the vocals.
Wherever your RealTracks you are using are:
bb\RealTracks\Data\Style Demos Audio
render the demo style sgu to a short wma (without count-in) then rename it to the style name eg: _ACCNTRY.wma
This is already the default... none of the local Style Demos Audio files have vocals - at least not that I am aware of. If you do not have the local demo (in C:\bb\RealTracks\Data\Style Demos Audio) for whatever reason, for example if you don't actually have the STY, then in that case yes you will hear the online demo which could have vocals if the style was used in an Artist Performance track.