Joe Truskot hosts with synopsis and commentary:  July 21 – Tosca with Callas, di Stefano; and July 28 – Turandot with Nilsson, Corelli. 7 – 10 p.m. on 90.7 Santa Cruz – 89.7 Monterey Salinas Watsonville – 89.5 Carmel Valley, Salinas Valley and online at ksqd.org. We aired last Monday: July 14 – La bohème with Pavarotti, Freni.