It's been almost 50 years since the tragically untimely death of Janis Joplin, whose rock, soul and blues set the standard for a whole generation of musicians who followed. 

About 30 years ago, I met Janis's younger sister Laura Joplin, who had just published a biography of Janis, based largely on a cache of letters her sister wrote, back in the day.

As she told me in this interview, it became a project she needed to do.