What I mean by extra-musical moments are times when something happens in the outside environment to enhance a piece of music that you are listening to, whether live or in person. I give you a list of four examples: 1) Seeing Leftover Salmon play "Breaking Through" live at an outdoor music festival. In the climax of the song a train comes barrelling behind the stage and lays on its horn 2) Sitting in my car during a rainstorm in August where the sun is still shining listening to Steve Reich's "Music for 18 Musicians." The shimmery light of sunshine combined with rain just made that piece make sense to me. 3) Having a jet fly over head during the really chilled out middle section of "La Villa Strangiato" at a Rush concert. 4) This morning, on my way to work, I was listening to Shostakovich's 4th Symphony, and this 18 wheeler hit a huge pothole right during a loud tympani roll. The jolt of the truck just added to the thunder of the percussion. Surely, someone else notices these kinds of things.
The organisers playing 'Jump around' in between bands at Reading as a guy in a wheelchair goes past. The South Park humour of the situation was not lost.
Walking down 33rd Street in NYC while listening to Radiohead's "Kid A", and the street noise that filtered through my headphones was in perfect synchronization with the music.