On Brattle Street, a jazzy serenade from a bunch of Squares By Daniel Gewertz Globe correspondent,Updated May 10, 2021, 2:59 p.m. Email to a Friend Bill Trabilcy emcees a Squares in the Square performance on a recent Saturday on Brattle Street in Harvard Square.Aram Boghosian for The Boston Globe Harvard Square has been a premiere spot for street performers for decades, but it took the COVID-era to produce a musical effort as enterprising as Squares in the Square. A weekend afternoon operation that pops up whenever the weather allows, a band led by saxophonist Bill Trabilcy often plays on Brattle Street for five straight hours. The Squares feature an array of guest singers, and a repertoire that easily switches from soul to swing, from pop to funk. The focus is on âaccessible jazzâ â no long, intellectual horn solos here. The band is expandable: basically a quintet, friends often join for a few numbers.