On the weekend of November 10 during the 2007–2008 Seattle Symphony season, the symphony performed both Brahms piano concerti and two of his symphonies in consecutive concerts. My subscription included one of them, and I bought a separate ticket to the other one, and the seat I was given was in the very front row.
You notice all sorts of things when you're in the very front row, things that elude your notice from even the second or third row. When you're that close, you're within an arm's reach of the musicians. I had to look away when the concertmaster bent over to tune the orchestra; otherwise I would've been looking up her dress. During the performance, I could read the music on the first violin's music stand. I could hear the pianist hum to himself. (And for some reason, pianists who hum also hum out of tune. Why is that?) And I could hear the conductor exhale through his teeth. It sounded like he was making quiet "choo choo" noises.
Then again, the "choo choo" noises might have been on purpose. He took the Brahms Fourth Symphony faster than I remember ever hearing it before. For all I know, the train noises were his way to get the orchestra to play faster.