Thu Dec 17, 2020 at 11:10 am By John von Rhein Chicago Symphony Orchestra members perform Dvořák’s Wind Serenade in Episode 9 of CSO Sessions. Photo: Todd Rosenberg Ten months into the Covid-19 pandemic, the Chicago Symphony Orchestra, in company with several other top-tier U.S. ensembles, is refusing to sing the lockdown blues. October 1 brought the debut of CSO Sessions, a set of hour-long chamber music concerts performed by members of the orchestra and filmed onstage the previous month at Orchestra Hall, Symphony Center. Available on demand at the organization’s website ( cso.org/csotv/cso-sessions),the series has thus far yielded nine “premium episodes”; a 10