Street Theatre Company’s ever-busy programming continues with yet another in its popular musicals-in-concert series. The latest is a strong choice, mainly because tuneful Broadway-originated pop-rock classics tend to hold their own. Meanwhile, the Hair story of ’60s-era hippies, political activism and anti-war protest might seem long ago and far away, but it’s interesting history and still delivers salient messages for us all about race, religion and personal freedom. We assume that all members of the STC ensemble will be keeping their clothes on for this staging, directed by Cathy Street with musical direction by Rollie Mains. The cast of more than 30 will render all of the show’s dialogue along with the score, the latter featuring radio hits aplenty, such as “Aquarius,” “Easy to Be Hard,” “Good Morning Starshine,” “Let the Sunshine In” (aka “The Flesh Failures”), and of course the excellent title tune, which was a huge Top 40 hit for (of all people) The Cowsills in 1969. The production is rated R due to strong themes and explicit language.