Jerusalem Baroque Orchestra All-Bach Program YMCA Auditorium April 9 An all-Bach instrumental and vocal program was presented this month by the Jerusalem Baroque Orchestra and conducted by David Shemer. Of course, a Bach program is always more than welcome, but the special attraction of this particular one was the rarely performed Cantata Nr. 51, "Be joyful in God in all lands," and the even more seldomly heard and extremely difficult Baroque trumpet. The cantata's aria was, in fact, a duet of soprano and trumpet. Keren Motseri trumpeted her clear, bright soprano - especially in the somewhat strained and shrill sounding higher register. Trumpeter David Kjar played his almost vocal-sounding solo part on his instrument with remarkable virtuosity. In Cantata Nr. 152, "Tread on the Road of Faith," Motseri was joined by Gabriel Loewenstein's appealing, somewhat high-timbred bass. On the more conventional level, the orchestra performed the Brandenburg Concerti Nrs. 2 and 4. The sonorities of the period instruments, quite different from those of the classic or modern ones, occasionally caused Lara Morris' and Benny Aghassi's lovely recorders to be overshadowed by the more assertive strings. Conductor Shemer will no doubt be able to achieve a more agreeable balance in future performances.