Few players in the jazz realm can satisfy every audience. There are traditionalists and there are progressives, and not often do the two meet. Ellyn Rucker, Sunday, July 22, at the Mercury Cafe, is a notable exception, a longtime local songstress whose music is easily as welcome on KUVO as it is on KHIH. Rucker's varied ability means she can play whenever and wherever she wants, whether it's appearing on Marian McPartland's Piano Jazz or trading fours with Bill Watrous or Dianne Reeves. Rucker is a silky vocalist and a confident pianist -- one of those rare types who demonstrate a complete command over both skills at the same time -- and she could easily have made a living doing either one. As much as she works (she has seventeen gigs in July alone), it's readily apparent she's doing something right.