The day was cold and wet, and more than a few lost souls sought refuge inside the Powell Street Station. The glow from an ad-free billboard illuminated LaVonne McIntosh as she banged out gospel tunes on a keyboard purchased for $50 at a thrift store. Read more at http://www.sfchronicle.com/bayarea/ci... Follow the City Exposed: facebook.com/cityexposedTwitter @cityexposedinstagram @cityexposed