How about an 90 minutes with Johann Sebastian Bach and three of his sons, featuring music from the 18th century, plus a much more modern Czech composer?  It is a well-thought out program of varied instrumentation, in the hands of Orchestra Iowa Chamber Player's talented musicians at the Opus Concert Cafe in downtown Cedar Rapids Friday evening. The program is an ideal one for chamber music lovers, but tough sledding for the uninitiated.   With the help of excellent program notes from Joseph and Elizabeth Kahn, however, it is bountiful beginning to baroque music, and to the Bach family esthetic.  A welcome curiousity on the bill of fare is the 20th century "neo-baroque" work by Ilja Hurnik.  It is complex piece, with shifting melodies and rhythmic surprises throughout.   It is a challenging work to perform, and the musicians were committed and ready:  Carey Bostian (cello), Jane Walker (flute), David Hempel (oboe), and Miko Konimani (harpsichord) were quite good.   I was grateful for the opportunity to hear this rarely performed work, and particularly enjoyed the second movement ("quasi marcia funebre").   I often enjoy the darker, slower movements.   As poet Margaret Hasse has written, "I like my coffee dark and sad." The first work on the program was by the elder Bach, represented by a rarely heard "reconstruction" by Robert Bridges.   Based on arias, the singing parts have been replaced by a violin-viola duo, and in the hands of Karla Galva and Lisa Ponton, it makes for intriguing music-making. Chamber music has been described as an intelligent conversation among very smart people.  These musicians were in earnest dialogue with each other, feeding off of each other beautifully.  The harpsichord in the J.S. Bach, however, was barely audible.  I could see that she was playing, but couldn't hear it.   Is the solution a larger harpsichord, or a better sense of balance with the other players? The highlight of the evening was by Bach's eldest son, Wilhelm Friedemann, "Sonata for Viola and Harpsichord in C Minor."  No problem with hearing the harpsichord here, and Lisa Ponton was in sync with Miko Kinomani, with stunning result. Ponton  plays with remarkable authority and depth, very secure in tone. Experience it for yourself Saturday at the Opus Concert Cafe at 7:30 p.m. and again Sunday at the Coralville Center for the Performing Arts at 2:30 p.m.