Geert Chatrou on stage (2005) as professional whistler
<a rel="nofollow" class="external text" href="https://www.flickr.com/people/51035756584@N01">Kars Alfrink</a> from Utrecht, Netherlands
CC BY 2.0
<a rel="nofollow" class="external text" href="https://www.flickr.com/photos/kaeru/22652991/">PINC.6</a>