There's nothing quite like a best friend. On Wednesday's Performance Today we'll hear two pieces by famous composer written for their less-famous closest confidantes. One piece is a horn concerto by Mozart composed for his friend Joseph Leutgeb. On the original music manuscript, Mozart scribbled in little notes to Leutgeb all through the music such as, "come on, quicken up here" and, "be a good fellow, have courage!" But at the end, Mozart wrote "thank heavens, that's enough, enough!"