There are three interesting happenings in the local art scene right now. This evening Mercer Union presents new compositions by Stephen Parkinson, a local musician who creates "do-it-yourself situations...with various friends as performers, reacting to a variety of methods of prescription/notation, involving toy instruments, electronics, vintage turntables, field recordings, as well as more traditional musical instruments." Tonight's various friends include Martin Arnold, Allison Cameron, Eric Chenaux, Rob Clutton, Aimée Dawn Robinson, and Doug Tielli. The......