The Pittsburgh Symphony Orchestra (PSO) is an American symphony orchestra, based at Heinz Hall in the Cultural District of Pittsburgh, Pennsylvania.Since 2005, this PSO has formally been lacking a single music director. During this current period, a new collective bargaining agreement was in effect, which gave the musicians increased authority over matters of running the orchestra such as the hiring of musicians and choice of repertoire. Read more on Last.fm. User-contributed text is available under the Creative Commons By-SA License; additional terms may apply.