The next time you are looking for surprises on YouTube, do not bypass Tommy Flanagan playing Billy Strayhorn’s “Rain Check.” The 1991 performance at a club in Germany was with his trio; George Mraz on bass, Bobby Durham on drums. The video and audio quality are unusually high for a YouTube clip, with matching direction and camera work. Flanagan’s Ellington quotes in his solo might be expected, but…”Star and Stripes Forever?”