It’s opening week for many American orchestras, and a new trend is emerging in response to the years of deficits plaguing so many ensembles: less star power, more homegrown talent. Research shows that a vast majority of the modern orchestra audience decides whether to attend a concert based on what’s being played, not on who’s playing it, so it hardly makes fiscal sense to spend tens of thousands of dollars on a big-name soloist who will only marginally increase the gate. In Minnesota, both of the Twin Cities’ major orchestras have bought into the idea of showcasing the ensemble rather than some traveling star, and the upcoming season will be an acid test of the attendance theory.