Negotiations on a new contract between Broadway producers and musicians began this week, and musician minimums are the big issue. The two sides are well apart. “Producers have taken what one source calls a ‘blood oath’ that they will hang together in the event of a strike. They expect the union to take a divide-and-conquer approach, striking only those shows with weak box offices or that don’t yet have their ‘virtual orchestras’ in place (there are a few). Should that happen, every show will bar musicians from the theater and use pre-recorded music.”