Classical MPR‘s Julie Amacher interviews the Pittsburgh Symphony’s principal horn, William (Bill) Caballero on New Classical Tracks! On the latest recording, Manfred Honeck leads the Pittsburgh Symphony Orchestra in two of Beethoven’s most popular symphonies, No. 5 and No. 7. Bill Caballero says what makes this recording remarkable is that it’s live. “So in one sense that’s a plus,” he says. “You’re getting a vibrant performance here. But what comes across in the recordings, which…