Though the name of this popular a capella group hasn’t changed since 1984, the faces and voices have. Seventy to 80 students have once carried the title of “Innocent Men” – also known as those guys who can harmonize extremely well, without the crutch of accompaniment. Jake Truby, a senior and current member of the  group, says over 50 of the former members have confirmed for an upcoming reunion concert. After e-mailing the invite, he says, “less than an hour later, people were responding.” One former crooner is trekking here from Boston, and many members will have families in tow. At the May 15 State Theatre concert, the current group performs first, followed by the first-ever Innocent Men, plus two other reunited groups. Surprisingly, Truby says, the repertoire hasn’t changed much over two and a half decades. For instance, Billy Joel is a classic, and has been for the longest time. “It’s been such a blast getting in touch with alumni – a lot of them haven’t changed a bit,” Truby says.