One of the jazz singers I would love to see play here, at RIJF or otherwise, is Kurt Elling. Kurt is a friend of one of my oldest friends. They met when he was just starting out on the singing career after a stint as a seminary student at the University of Chicago, my alma mater (in fact singing folk music at the time). The first time I saw Kurt perform was at Andy's jazz club near my office at the time in downtown Chicago. He had just signed with Blue Note at the time. I was floored by his vocalese, something I hadn't heard much of before (at that time I was more of a jazz novice). I saw him a number of times thereafter in Chicago clubs, especially the Green Mill (a former hangout of Capone on the North Side that was just a hop from my apartment in Evanston). On more than one occasion, I shared a table with my friend and Kurt between sets while he worked out the next set list and talked about jazz. It was an early exposure to why and how people do this music.
Here is a video off YouTube of Kurt singing The Waking in a live perfomance at the Fabryce Trzciny in Poland in 2005.
Kurt is always exploring; that's one of the things I like about his music. Not sure why we haven't seen him here (he played SUNY Potsdam earlier this year, I think), but perhaps RIJF 2008?