These days, as one-fourth of the throwback revue group Under the Streetlamp, Micahel Cunio knows that a certain era of music still has connective power. With their ranks comprised of veterans from the Chicago cast of the Broadway smash Jersey Boys — a jukebox musical dramatizing the rise to fame of Frankie Valli and the Four Seasons — the harmonic vocalists pay homage to familiar hits that Cunio described as the “American radio songbook.”