Not free, but when I lived in the 'Burgh back in the day, every major act came through, in part due to the 'connected' promoters, and the fact that it was a big enough city to accomodate large crowds in big venues. Here's a list that reflects just one (although probably the biggest) promoter's shows back in the day. Saw many, not all of these shows. Sadly, the acoustics at the Civic Arena, where many took place, were pretty bad. The Stanley is still vital there, I trust and the Syria Mosque, long turned to rubble.
http://dicesare-englerproductions.com/Pittsburgh_Rock_Concerts.php
http://dicesare-englerproductions.com/Pittsburgh_Rock_Concerts.php