In reading the various responses, it brings to mind many magical musical moments in my life.
Hearing The Immigrant Song by Led Zeppelin when it was released in 1970: since I've always considered LZ a forerunner to today's metal, this was an important turn in my muscial tastes, taking me away from The Beatles, The Dave Clark Five, and others. Other bands followed, like Aerosmith & Metallica, but until Opeth arrived on my scene, no other band had impact on me like Led Zeppelin did.
I've been to only two pop band concerts, and both were when the artists were at their peak - Ricky Martin and Alanis Morrissette. It was more of the fans reactions that caught my eye and got me close to pop music and its effect on people. There was the excited jumping for joy kidlike emotions that you don't see at metal concerts. It didn't seem that the reactions were about the music, but only about the person behind the music. Personally, I thought Ricky Martin put on a great "show".
Seeing Arthur Fiedler and The Boston Pops play my favorite classical song, Bolero, was something special.
When I was 12, my Dad had donated $200 to a TV station, which in turn bought me 1 hours playing time with the organist of The Boston Pops. There I was, at Symphony Hall in Boston, playing this organ and it's amazing pipes. It was a trip.
Best pop music moment for me - seeing Ashlee Simpson make a lip synching fool of herself on Saturday Night live, then playing an awful performance at halftime at the Orange Bowl. Pop music at its best.